After installing an IPW2200 mini-pci 802.11g wireless card, my wife complained that her system would freeze for a minute while attempting to connect to an 802.11 (WEP) network for the first time. After the initial time-out and failure, wireless network connections would work fine until the computer was rebooted. 

As it turns out, I was experiencing the same problems with my laptop, but I hadn't noticed it because I use suspend/resume a lot more than my wife, and I would go a week or so before doing a full reboot. (One failure to connect to a wireless network per week is a lot less noticeable than one every morning.)

After doing a lot of rebooting and troubleshooting, I isolated a few lines in my /var/log/syslog that appeared to be associated with the freezeup:

eth2: could not initialize WEP: load module ieee80211_crypt_wep

ieee80211_crypt_wep: could not allocate crypto API arc4

Even though my system (Ubuntu 7.04) had the arc4 crypto module, it didn't appear to be loading correctly. I added "arc4" to my /etc/modules file to force it to be loaded, and that appears to have fixed the problem.