Since when does this happen? I have no idea how such a shortcut with "Shift" can be created accidentally. Does it make a difference whether you press "Shift" in your browser or in Notepad?
You can change your keyboard-layout here:
Control Panel -> Regional and Language Options -> Languages -> Details
Does it make a difference if you choose another keyboard layout?
Make sure your SpacePilot Shift key is really assigned to Shift in the 3DxWare driver. It may be assigned to 3DxHelp or something like that. Still, that wouldn't trigger anything from the actual keyboard shift key. We don't touch the actual keyboard shift key.
This is since a week or 2 - 3.
I'm sure I haven't changed anything on purpose myself, though I know there are other people using my computer when I'm not present.
Just reinstalled the driver and that solved the problem.
Gonna keep my eyes open when other people are using my computer in the future