Ripping to WMA in WMP 10

I used to be able to rip all my cds to WMA, but switched to MP3. I tried
switching back to WMA, but I get the message "Windows Media Player
encountered an unknown error. This can occur when another program or
operating system encounters a problem but does not communicate the nature of
the problem to the player." I have also deleted music that was originally
recorded as WMA, but now they won't record as anything but MP3. I am able to
use the variable WMA rate, but not the regular WMA. I am currently using WMP
10.00.00.4074, Windows XP Media Center Service Pack 3. Any help would be
appreciated. Thanks!