No wireless connection with security

About 3 weeks ago, the wireless connection to one of our machines suddenly
stopped working after over a year of normal operation. a year. We changed
nothing in the network setup. We were usinig WPA so in an effort to
troubleshoot, we disabled security and it connected. When we try to
re-enable WPA or use WEP though, the machine is unable to connect.

I looked at the Windows Update log and noticed that there were some OS
security patches downloaded around the time things went bad. Are there any
known issues is this area?

Thanks.