Odd keyboard behavior

[Dosick, Daniel (GE EntSol, Security)]

FM8 (patch 277), WinXP pro
 
This one's pretty bizarre: 
As of a couple of days ago (I think), when I type a single or double
quotation mark (' or ") in Frame 8, a question mark appears rather than
the quotation mark character. 
Changing the font has no effect. All the other keys do just what they're
supposed to do. 
This is only happening in FM8, not in FM7.1 or in any other application
I've tried. 
Any ideas?
Thanks.