I did a few things before I was going to go and restore some preferences, which began as a repair permissions, a logout and back in, but to no avail.
But you are right, a restart fixed this issue, it seems.
I normally go through a process before I try and fix a problem:
1) Visit console
(in this case, I had a strange error:
26/10/08 1:55:37 PM configd[34] Error: get APPLE80211_IOC_POWERSAVE failed, -4 (Operation not supported) , which popped up every minute exactly)
2) Google any errors.
(this error brought me to an apple.discussion:
http://discussions.apple.com/thread.jspa?messageID=8346031 , interestingly it was related to issues with the Airport update 2008-003)
It suggested to delete some system preferences and reboot in safe mode)
3) repair permissions
4) log out, and back in
5) restart
This got me going again, though I have this error in the log:
26/10/08 2:12:08 PM mDNSResponder[21] Note: Frequent transitions for interface en1 (FE80:0000:0000:0000:021E:C2FF:FEBA:435A); network traffic reduction measures in effect
Not sure what this is, but since I'm ok, I guess I can leave it.
I normally do the above steps before attempting any serious fix. I guess I'm lucky it worked for me until here.