I'm currently at the Hong Kong Airport.  Free wifi is offered and I believe there are multiple AP transparently networked together.  I am using a 1001P netbook and the wifi is unstable, reconnecting about every 30 seconds.  Judging from the syslog it looks like this is due to failed roaming ("Roamed to ... none").  Obviously, I will not be able to repeat this problem after today.

lspci:
02:00.0 Network controller: Atheros Communications Inc. Device 002c (rev 01)
	Subsystem: Device 1a3b:1112
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 32 bytes
	Interrupt: pin A routed to IRQ 17
	Region 0: Memory at fbff0000 (64-bit, non-prefetchable) [size=64K]
	Capabilities: <access denied>
	Kernel driver in use: ath9k
	Kernel modules: ath9k

$ grep Roam.*HKAir /var/log/syslog -3
Jul 17 18:58:40 localhost avahi-daemon[1045]: New relevant interface wlan0.IPv4 for mDNS.
Jul 17 18:58:40 localhost avahi-daemon[1045]: Registering new address record for 192.168.61.145 on wlan0.IPv4.
Jul 17 18:58:41 localhost NetworkManager: <info>  (wlan0): device state change: 7 -> 8 (reason 0)
Jul 17 18:58:41 localhost NetworkManager: <debug> [1342522721.093985] periodic_update(): Roamed from BSSID E8:BA:70:C3:EF:21 (#HKAirport Free WiFi) to 08:17:35:C7:2E:A0 (#HKAirport Free WiFi)
Jul 17 18:58:41 localhost NetworkManager: <info>  Policy set 'Auto #HKAirport Free WiFi' (wlan0) as default for routing and DNS.
Jul 17 18:58:41 localhost NetworkManager: <info>  Activation (wlan0) successful, device activated.
Jul 17 18:58:41 localhost NetworkManager: <info>  Activation (wlan0) Stage 5 of 5 (IP Configure Commit) complete.
--
Jul 17 18:59:45 localhost kernel: [ 1172.737870] wlan0: authenticate with 08:17:35:c7:2e:a0 (try 2)
Jul 17 18:59:45 localhost kernel: [ 1172.937865] wlan0: authenticate with 08:17:35:c7:2e:a0 (try 3)
Jul 17 18:59:45 localhost kernel: [ 1173.137881] wlan0: authentication with 08:17:35:c7:2e:a0 timed out
Jul 17 18:59:46 localhost NetworkManager: <debug> [1342522786.430972] periodic_update(): Roamed from BSSID 08:17:35:C7:2E:A0 (#HKAirport Free WiFi) to (none) ((none))
Jul 17 18:59:47 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  completed -> disconnected
Jul 17 18:59:47 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  disconnected -> scanning
Jul 17 18:59:47 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  scanning -> associating
--
Jul 17 19:02:53 localhost avahi-daemon[1045]: New relevant interface wlan0.IPv4 for mDNS.
Jul 17 19:02:53 localhost avahi-daemon[1045]: Registering new address record for 192.168.61.145 on wlan0.IPv4.
Jul 17 19:02:54 localhost NetworkManager: <info>  (wlan0): device state change: 7 -> 8 (reason 0)
Jul 17 19:02:54 localhost NetworkManager: <debug> [1342522974.469060] periodic_update(): Roamed from BSSID E8:BA:70:C3:EF:21 (#HKAirport Free WiFi) to 08:17:35:C7:2E:A0 (#HKAirport Free WiFi)
Jul 17 19:02:54 localhost NetworkManager: <info>  Policy set 'Auto #HKAirport Free WiFi' (wlan0) as default for routing and DNS.
Jul 17 19:02:54 localhost NetworkManager: <info>  Activation (wlan0) successful, device activated.
Jul 17 19:02:54 localhost NetworkManager: <info>  Activation (wlan0) Stage 5 of 5 (IP Configure Commit) complete.
--
Jul 17 19:03:34 localhost kernel: [ 1402.293177]     (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm)
Jul 17 19:03:36 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  associating -> associated
Jul 17 19:03:36 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  associated -> completed
Jul 17 19:03:38 localhost NetworkManager: <debug> [1342523018.003442] periodic_update(): Roamed from BSSID 08:17:35:C7:2E:A0 (#HKAirport Free WiFi) to 08:17:35:C6:F4:71 (#HKAirport Free WiFi)
Jul 17 19:03:55 localhost wpa_supplicant[1140]: Trying to associate with 08:17:35:c7:2e:a0 (SSID='#HKAirport Free WiFi' freq=2462 MHz)
Jul 17 19:03:55 localhost kernel: [ 1422.739252] wlan0: deauthenticating from 08:17:35:c6:f4:71 by local choice (reason=3)
Jul 17 19:03:55 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  completed -> associating
--
Jul 17 19:03:55 localhost kernel: [ 1422.775211]     (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:03:55 localhost kernel: [ 1422.775226]     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:03:55 localhost kernel: [ 1422.775242]     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:03:56 localhost NetworkManager: <debug> [1342523036.229992] periodic_update(): Roamed from BSSID 08:17:35:C6:F4:71 (#HKAirport Free WiFi) to (none) ((none))
Jul 17 19:04:05 localhost wpa_supplicant[1140]: Authentication with 00:00:00:00:00:00 timed out.
Jul 17 19:04:05 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  disconnected -> scanning
Jul 17 19:04:06 localhost wpa_supplicant[1140]: Trying to associate with 08:17:35:c6:f4:71 (SSID='#HKAirport Free WiFi' freq=2462 MHz)
--
Jul 17 19:04:07 localhost kernel: [ 1434.843048] cfg80211: Current regulatory domain updated by AP to: HK
Jul 17 19:04:07 localhost kernel: [ 1434.843060]     (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
Jul 17 19:04:07 localhost kernel: [ 1434.843075]     (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm)
Jul 17 19:04:08 localhost NetworkManager: <debug> [1342523048.134885] periodic_update(): Roamed from BSSID (none) ((none)) to 08:17:35:C6:F4:71 (#HKAirport Free WiFi)
Jul 17 19:04:10 localhost NetworkManager: <info>  (wlan0): device state change: 8 -> 3 (reason 11)
Jul 17 19:04:10 localhost NetworkManager: <info>  (wlan0): deactivating device (reason: 11).
Jul 17 19:04:10 localhost NetworkManager: <info>  (wlan0): canceled DHCP transaction, dhcp client pid 4659
--
Jul 17 19:05:08 localhost avahi-daemon[1045]: New relevant interface wlan0.IPv4 for mDNS.
Jul 17 19:05:08 localhost avahi-daemon[1045]: Registering new address record for 192.168.61.145 on wlan0.IPv4.
Jul 17 19:05:09 localhost NetworkManager: <info>  (wlan0): device state change: 7 -> 8 (reason 0)
Jul 17 19:05:09 localhost NetworkManager: <debug> [1342523109.131201] periodic_update(): Roamed from BSSID 08:17:35:C7:E8:41 (#HKAirport Free WiFi) to 08:17:35:C6:F9:91 (#HKAirport Free WiFi)
Jul 17 19:05:09 localhost NetworkManager: <info>  Policy set 'Auto #HKAirport Free WiFi' (wlan0) as default for routing and DNS.
Jul 17 19:05:09 localhost NetworkManager: <info>  Activation (wlan0) successful, device activated.
Jul 17 19:05:09 localhost NetworkManager: <info>  Activation (wlan0) Stage 5 of 5 (IP Configure Commit) complete.
--
Jul 17 19:06:15 localhost kernel: [ 1563.544263]     (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:06:15 localhost kernel: [ 1563.544276]     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:06:15 localhost kernel: [ 1563.544289]     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:06:20 localhost NetworkManager: <debug> [1342523180.001628] periodic_update(): Roamed from BSSID 08:17:35:C6:F9:91 (#HKAirport Free WiFi) to (none) ((none))
Jul 17 19:06:25 localhost wpa_supplicant[1140]: Authentication with 00:00:00:00:00:00 timed out.
Jul 17 19:06:25 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  disconnected -> scanning
Jul 17 19:06:26 localhost wpa_supplicant[1140]: Trying to associate with 08:17:35:c7:35:91 (SSID='#HKAirport Free WiFi' freq=2437 MHz)
--
Jul 17 19:06:43 localhost avahi-daemon[1045]: New relevant interface wlan0.IPv4 for mDNS.
Jul 17 19:06:43 localhost avahi-daemon[1045]: Registering new address record for 192.168.61.145 on wlan0.IPv4.
Jul 17 19:06:44 localhost NetworkManager: <info>  (wlan0): device state change: 7 -> 8 (reason 0)
Jul 17 19:06:44 localhost NetworkManager: <debug> [1342523204.007847] periodic_update(): Roamed from BSSID E8:BA:70:F8:03:91 (#HKAirport Free WiFi) to 08:17:35:C6:F9:91 (#HKAirport Free WiFi)
Jul 17 19:06:44 localhost NetworkManager: <info>  Policy set 'Auto #HKAirport Free WiFi' (wlan0) as default for routing and DNS.
Jul 17 19:06:44 localhost NetworkManager: <info>  Activation (wlan0) successful, device activated.
Jul 17 19:06:44 localhost NetworkManager: <info>  Activation (wlan0) Stage 5 of 5 (IP Configure Commit) complete.
--
Jul 17 19:06:55 localhost kernel: [ 1603.520950]     (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:06:55 localhost kernel: [ 1603.520965]     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:06:55 localhost kernel: [ 1603.520981]     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jul 17 19:06:56 localhost NetworkManager: <debug> [1342523216.224824] periodic_update(): Roamed from BSSID 08:17:35:C6:F9:91 (#HKAirport Free WiFi) to (none) ((none))
Jul 17 19:06:58 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  associating -> disconnected
Jul 17 19:07:05 localhost wpa_supplicant[1140]: Authentication with 00:00:00:00:00:00 timed out.
Jul 17 19:07:05 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  disconnected -> scanning
--
Jul 17 19:07:45 localhost kernel: [ 1654.045086] wlan0: associate with 08:17:35:c6:f9:91 (try 2)
Jul 17 19:07:45 localhost kernel: [ 1654.245076] wlan0: associate with 08:17:35:c6:f9:91 (try 3)
Jul 17 19:07:46 localhost kernel: [ 1654.445225] wlan0: association with 08:17:35:c6:f9:91 timed out
Jul 17 19:07:50 localhost NetworkManager: <debug> [1342523270.001365] periodic_update(): Roamed from BSSID 08:17:35:C6:F9:91 (#HKAirport Free WiFi) to (none) ((none))
Jul 17 19:07:55 localhost wpa_supplicant[1140]: Authentication with 08:17:35:c6:f9:91 timed out.
Jul 17 19:07:55 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  associating -> disconnected
Jul 17 19:07:55 localhost NetworkManager: <info>  (wlan0): supplicant connection state:  disconnected -> scanning
--
Jul 17 19:12:03 localhost avahi-daemon[1045]: New relevant interface wlan0.IPv4 for mDNS.
Jul 17 19:12:03 localhost avahi-daemon[1045]: Registering new address record for 192.168.61.145 on wlan0.IPv4.
Jul 17 19:12:04 localhost NetworkManager: <info>  (wlan0): device state change: 7 -> 8 (reason 0)
Jul 17 19:12:04 localhost NetworkManager: <debug> [1342523524.549428] periodic_update(): Roamed from BSSID E8:BA:70:C3:EF:21 (#HKAirport Free WiFi) to E8:BA:70:C3:EE:91 (#HKAirport Free WiFi)
Jul 17 19:12:04 localhost NetworkManager: <info>  Policy set 'Auto #HKAirport Free WiFi' (wlan0) as default for routing and DNS.
Jul 17 19:12:04 localhost NetworkManager: <info>  Activation (wlan0) successful, device activated.
Jul 17 19:12:04 localhost NetworkManager: <info>  Activation (wlan0) Stage 5 of 5 (IP Configure Commit) complete.