Gee so glad to know that my network has been compromised. I now need to jump up and run around in circles going crisis crisis crisis. Wow I feel much better now.
This has been plaguing my Macbook every time it wakes up from sleep since Leopard 10.5.1 came out. I have not tested 10.5.2 yet to see if it fixes the problem. It seems to occur when I am connecting to WRT54G's running the DD-WRT firmware using WDS. This allows multiple wireless access points to look sort of like one access point and extend the range of your access point. It also appears to be centered around using WPA.
My solution. Well running around in circles going crisis crisis crisis can be fun but it really did not solve the problem. Rebooting would fix it but gee that takes a bit. Googling came up with a forum on Macrumors that suggested deleting the saved password. I can't remember if I found another link or just did it wrong but here is what I did.
Removed the offending network from the list of preferred networks. Now when I put the Macbook to sleep it wakes up and asks which network do I want to connect to, I double click on the one I was using and bam I'm on the network again no silly error.
Nope 10.5.2 does not fix the problem.