Copy/Paste locks up Excel 2007

Hi-

I have an Excel spreadsheet (in the .xls 97-2003 format) that I have been working with on a PC running Microsoft XP sp3 with Office 2007 sp1 installed.  This is a file that has been copy/pasted to multiple times.  The problem I am having is that the copy and paste commands have started to take a long time to complete and occassionally freeze up Excel to the point that I have to kill the program in Task Manager.  I am not copying huge amounts of data, just maybe 4 or 5 lines at a time.  And all copying and pasting is being done on the local computer and within the spreadsheet, so its not an issue of moving data between different workbooks or working with a file on a network share.  The file is decent size, not massively huge by any means, only about 3 or 4 mb.

The really weird thing is that even if I just open the workbook, copy/paste a couple of lines, and then go to close it, I get a message saying "There is a large amount of information on the clipboard."  This makes me think Excel is somehow remembering all of the old copy and pastes.  I have tried to open this spreadsheet on several PCs running Office 2007 and all show the same issue.  I tried opening it on a PC that uses Excel 2003 and copy/paste works just fine with no delays.  Unfortunately, using Office 2003 is not really an option to solve this problem because this user's PC came with Office 2007 OEM on it and we don't really have any spare Office 2003 discs with retail licenses lying around that we could throw on there.

I've also tried saving it out as an .xlsx 2007 Office format file and the problem persists.  I've tried copying the data off to a new spreadsheet and the new spreadsheet works fine for a while, but the issue resurfaces after several copy/pastes are made in the new spreadsheet.  I've also tried turning off my antivirus protection (we use McAfee) and the problem still persists.

I've looked all over Microsoft's website and done several searches on various tech support forums, but have come up with nothing.  Anyone else seeing this problem?  If so, were you able to resolve it and how?

Thanks,

Hans