I have a very similar problem to the one metioned above, but it happens entirely randomly!
I know it's not my keyboard because it's happened on 2 different keyboards now. As a matter of fact I got a brand new keyboard because I thought that the old one was wonky due to this problem :S
So anyway, brand spanking new keyboard, same old problem.
I never had this problem on my old computer, but I got a new computer packaged with Vista...
It happens entirely randomly. I'm sure my regional settings are changed somehow/somewhere, but I don't know how or where! One second I'll be playing World of Warcraft typing /1 text, the next it'll be accented E text. When I go back to MSN my keyboards fine, it just happens in WoW.
... then of course, there's the complete opposite scenario, where in windows and MSN my ? turns into an accented E, but WoW is fine.
Does windows have some silly command to change the regional settings on your keyboard? I use CTRL and SHIFT a lot while playing in WoW in combination with custom hotkeys, could I be accidentally hitting some regional keyboard changing thingy?