WEP, WPA and Windows XP/SP2

Greetings all...a couple of issues...

I am told that WEP and Windows XP2 have some connectivity issues at times. Is this true ? I have tried to change teh security setting of the APX to WPA2 Personal, to enable the PC to connect (PC can't connect to internet, but can connect to network when it is set to WEP). When I set it to WPA then neither the G4 nor the PC connects.

Do I have to do anything else once I change the security settings on the ABS besides restarting ?

Thanks for the help !