Same unstable behavior here. Fresh install of Ubuntu 9.04 and updated system.
The wireless network is not protected (no WPA or WPE, nothing).
With Ubuntu 8.04 everithing worked fine but with 9.04 it is very difficult to get connected.
After many (~20) trials of wirleless connections aborted, the system, sometimes, get connected but for few seconds. Then everything starts again (20 trials, then connected for few seconds)
Sometimes, I can get connected for longer time without device deactivation (see logs), but with continuous associaton and disconnection steps)
I tried another NIC (Broadcom 4306 with restricted drivers) and it is worst :(
 
Here some details:
 
Network controller: Intel Corporation PRO/Wireless 2200BG [Calexico2] Network Connection (rev 05)
	Subsystem: Intel Corporation Device 2701
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 64 (750ns min, 6000ns max), Cache Line Size: 32 bytes
	Interrupt: pin A routed to IRQ 19
	Region 0: Memory at ffcfe000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [dc] Power Management version 2
		Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
		Status: D0 PME-Enable- DSel=0 DScale=1 PME-
	Kernel driver in use: ipw2200
	Kernel modules: ipw2200


tail /var/log/syslog
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1) starting connection 'Auto Default' 
May 17 14:45:51 VirteX NetworkManager: <info>  (eth1): device state change: 3 -> 4 
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1) Stage 1 of 5 (Device Prepare) scheduled... 
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1) Stage 1 of 5 (Device Prepare) started... 
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1) Stage 2 of 5 (Device Configure) scheduled... 
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1) Stage 1 of 5 (Device Prepare) complete. 
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1) Stage 2 of 5 (Device Configure) starting... 
May 17 14:45:51 VirteX NetworkManager: <info>  (eth1): device state change: 4 -> 5 
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1/wireless): connection 'Auto Default' requires no security.  No secrets needed. 
May 17 14:45:51 VirteX NetworkManager: <info>  Config: added 'ssid' value 'Default' 
May 17 14:45:51 VirteX NetworkManager: <info>  Config: added 'scan_ssid' value '1' 
May 17 14:45:51 VirteX NetworkManager: <info>  Config: added 'key_mgmt' value 'NONE' 
May 17 14:45:51 VirteX NetworkManager: <info>  Activation (eth1) Stage 2 of 5 (Device Configure) complete. 
May 17 14:45:51 VirteX NetworkManager: <info>  Config: set interface ap_scan to 1 
May 17 14:45:51 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> scanning 
May 17 14:45:51 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  scanning -> associating 
May 17 14:45:51 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:45:56 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:45:58 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:00 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:02 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:04 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:05 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:07 VirteX NetworkManager: <info>  eth1: link timed out. 
May 17 14:46:08 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:08 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:13 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:15 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:16 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> scanning 
May 17 14:46:16 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  scanning -> associating 
May 17 14:46:18 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:21 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:21 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:24 VirteX NetworkManager: <info>  eth1: link timed out. 
May 17 14:46:25 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:35 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:39 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> scanning 
May 17 14:46:44 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  scanning -> disconnected 
May 17 14:46:44 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:47 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:48 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  disconnected -> associating 
May 17 14:46:50 VirteX NetworkManager: <info>  (eth1): supplicant connection state:  associating -> disconnected 
May 17 14:46:51 VirteX NetworkManager: <info>  Activation (eth1/wireless): association took too long, failing activation. 
May 17 14:46:51 VirteX NetworkManager: <info>  (eth1): device state change: 5 -> 9 
May 17 14:46:51 VirteX NetworkManager: <info>  Activation (eth1) failed for access point (Default) 
May 17 14:46:51 VirteX NetworkManager: <info>  Marking connection 'Auto Default' invalid. 
May 17 14:46:51 VirteX NetworkManager: <info>  Activation (eth1) failed. 
May 17 14:46:51 VirteX NetworkManager: <info>  (eth1): device state change: 9 -> 3 
May 17 14:46:51 VirteX NetworkManager: <info>  (eth1): deactivating device (reason: 0).