Windows 7 - WMP12 won't run on win7 64bit

This problem started in last couple of days for no obvious reason.

Machine seems to run fun but as soon as I load WMP12 the probs start....

It either won't load - I get the outline of the WMP12 window but the content is all white and it just sits there. When this is happening other progs slow down and some stop responding such as Firefox. After a long wait I did mangage to get WMP loaded and once there it ran fine. However, when I quit and tried to reload the same prob happened again.

When I load WMP I hear disc activity as would happen suring a normal load - but the screen stays blank. Also, I sometime get 'not responding' on the title bar of the window. I thien have to clear using task manager.

Things I've tried:

System restore to before the fault - no difference
Uninstalled the shark007 codecs I had - now running without them - no difference.
Reinstated the WMP defaults using the MSoft tool - no difference
'uninstalled' WMP using the windows preferences, re boots and reinstalled again - no change
Rebuilt the library in case it was corrupt - no difference.

Hope someone can point me the right way....

This is a Win 7 home premium machine, 12gb ram, ATI Radion HD5670 graphics card.

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Update - have subsequently done some more testing...

If I delete the library so it has to rebuild it starts fine everytime. However, when I restart with a library in place it does as described above - I assume therefore it's a corruption/access issue?