User had a spreadsheet open and had pasted data from
another spreadsheet and added some worksheets - had been
working for 3 hours and had not saved......error message
Excel.exe has generated errors and will be closed by
Windows.  And then it closes.   Any ideas why this
happened?  It is a new system plenty of memory, and hard
drive space....service pack 3 has been installed.....would
appreciate any input.....want to know what caused it so I
can try to prevent it from happening again.

Thanks so much.