Bizarre Win7 problem with keyboard shortcuts

[manveruppd]

I'm on 7 Home Premium, and today half of Windows's keyboard shortcuts have stopped working! Specifically all the Windows Logo Key + arrow key shortcuts don't work, whereas everything else does!
I haven't installed ANY new programs, so it's really doing my head in what might've possibly caused this!

 

[gillywibble]

Have you tried a different keyboard to rule out a hardware issue?

Virus scan? Checked your keyboard settings in control panel? Has anything been spilled on it?

 

[manveruppd]

Nothing like that, as the arrow keys work fine by themselves, as does the Windows key by itself (or in combination with other shortcut keys like Win+D to minimise everything), only when you combine Win+arrow keys does nothing happen... I've been rooting around in Control Panel trying to find out if I've accidentally disabled them but can't find the relevant options anywhere.
Got AntiVir installed and did a scan earlier, didn't find anything at all, and it doesn't seem like the kind of thing a virus would do anyway...
It's truly BIZARRE!!!