Weird problem..I can't pinpoint the source

I have successfully implemented a wireless home network using a linksys
WRT54G and activated WPA-AES on 3 PCs (with the MS WPA patch).

Just now, all the connections were lost, and the problem is this: I checked
the Preferred networks entry's properties on the Windows XP clients and
couldn't find WPA-PSK and AES (and etc.) on the list except those ones
included before applying the WPA patch (WEP). I couldn't get them again so I
just re-installed the WPA patch.

So I don't know what happened here.