This is highly unlikely but you cannot copy and paste in Quick Mask mode-so is that on? How about this weeks update of Photoshop, have you installed that? What size are the graphics you are attempting to cut and paste-could it be you are running out of memory?
If the problem affects earlier versions then do you have any utility monitoring the clipboard? There are fancy things available like Clipmate that allow multiple clipboards to exist. We have established 'export to clipboard' is enabled in Photoshop as it definitely won't work without that being on.
I have tried to reproduce your problem on my system without success and also have not seen reports of anything similar online, so it seems to me a system specific issue-which makes it tough to diagnose from afar. Hi, I see this remains unresolved after 10 days.
