I have a HP Elitebook 2730p. lspci shows my WLAN adapter as follows:

02:00.0 Network controller: Intel Corporation PRO/Wireless 5100 AGN [Shiloh] Network Connection

When I am at home (WPA2) everything works perfect. But when I am at work (WEP 128 with shared key), I never get a working connection. The strange thing is that all my other machines at work (all running Ubuntu 8.10 but all with a different WLAN adapter) get a connection without any problem. Therefore my guess is that something is broken in the iwlagn driver that does not like WEP or shared keys. But I am no expert here at all. Here are some more details about the machine where the connection fails:

Here is the output of iwconfig:
wlan0     IEEE 802.11abgn  ESSID:""  
          Mode:Managed  Frequency:2.462 GHz  Access Point: Not-Associated   
          Tx-Power=15 dBm   
          Retry min limit:7   RTS thr:off   Fragment thr=2352 B   
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

Here is the output of iwlist scan:
wlan0     Scan completed :
          Cell 01 - Address: 00:11:92:EE:62:A0
                    ESSID:""
                    Mode:Master
                    Channel:11
                    Frequency:2.462 GHz (Channel 11)
                    Quality=96/100  Signal level:-32 dBm  Noise level=-127 dBm
                    Encryption key:on
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 6 Mb/s; 9 Mb/s
                              11 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s; 36 Mb/s
                              48 Mb/s; 54 Mb/s
                    Extra:tsf=00000c42cb7b618f
                    Extra: Last beacon: 24ms ago

When I kill nm-applet and start it from the command line, I get the following console output after the connection failed:
** Message: <info>  New secrets for PFHSO_PWLAN/802-11-wireless-security requested; ask the user

dmesg shows the following lines:
[  150.885106] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  151.084108] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  151.284312] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  151.484145] wlan0: authentication with AP 00:11:92:ee:62:a0 timed out
[  160.896064] iwlagn: index 0 not used in uCode key table.
[  167.673256] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  167.872305] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  168.072054] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  168.272302] wlan0: authentication with AP 00:11:92:ee:62:a0 timed out
[  177.684041] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  177.688083] iwlagn: index 0 not used in uCode key table.
[  177.884304] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  178.084310] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  178.284307] wlan0: authentication with AP 00:11:92:ee:62:a0 timed out
[  194.442731] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  194.640149] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  194.840310] wlan0: authenticate with AP 00:11:92:ee:62:a0
[  195.040318] wlan0: authentication with AP 00:11:92:ee:62:a0 timed out

Here is the content of /var/log/wpa_supplicant.log:
CTRL-EVENT-SCAN-RESULTS 
CTRL-EVENT-SCAN-RESULTS 
CTRL-EVENT-SCAN-RESULTS 
CTRL-EVENT-SCAN-RESULTS 
CTRL-EVENT-SCAN-RESULTS 
Trying to associate with 00:11:92:ee:62:a0 (SSID='PFHSO_PWLAN' freq=2462 MHz)
Authentication with 00:11:92:ee:62:a0 timed out.
CTRL-EVENT-SCAN-RESULTS 
CTRL-EVENT-SCAN-RESULTS 
Trying to associate with 00:11:92:ee:62:a0 (SSID='PFHSO_PWLAN' freq=2462 MHz)
CTRL-EVENT-SCAN-RESULTS 
Authentication with 00:11:92:ee:62:a0 timed out.
CTRL-EVENT-SCAN-RESULTS 
Trying to associate with 00:11:92:ee:62:a0 (SSID='PFHSO_PWLAN' freq=2462 MHz)
Authentication with 00:11:92:ee:62:a0 timed out.
CTRL-EVENT-SCAN-RESULTS 
CTRL-EVENT-SCAN-RESULTS 
Trying to associate with 00:11:92:ee:62:a0 (SSID='PFHSO_PWLAN' freq=2462 MHz)
Authentication with 00:11:92:ee:62:a0 timed out.
CTRL-EVENT-SCAN-RESULTS 
CTRL-EVENT-SCAN-RESULTS