I have had a similar problem on a new, plenty-fast i7 machine. Even with a trivial spreadsheet with half a dozen cells and one formula, Ctrl-C would freeze Excel for 20-30 seconds. I, however, would always get control back after that time. Turned out to be something to do with default printer. My default was a network printer that was offline. When I went to control panel and changed my default printer to CutePDF writer or something like that, copies became instantaneous as they should be.
