[Pepper]

This is definitely your issue, not a game issue. Something this huge would have come up sooner if it effected even a slightly substantial portion of people.

My shift key works fine in both fullscreen and windowed mode (I never used windowed, but did check).

I suspect your drivers are not up to date? What vid card are you using? Try to update all your drivers (video, chipset, mobo) and make sure you directX is up to date.

Thats a strange issue, regardless!