This is a strange issue and i'll try to explain as best possible. I have a spreadsheet called inventory.xls that I created in Excel 2003. All the users on Excel 2007 or Excel 2010 are able to view it but when they click the worksheet tabs it either does not click or clicks the adjacent tab but not the correct one ever. This is very strange. All users are on Windows-based PCs with wired keyboard and mouse and Windows XP or 7. The worksheet tabs click fine in Excel 2003 this is only in 2007 or 2010. Any ideas?