This is a quirk in Excel that we have not been able to solve for all cases. You have two choices to work around this problem:

(1) Open both files with macros disabled. See our knowledgebase article on macros for further information.

(2) Use the Office Clipboard (Excel 2000 or later) to copy and paste. Open the Office Clipboard by choosing Edit - Office Clipboard from the Excel menu. It opens as a sidebar to the Excel window.