File access error in Excel
 

I just started having a weird problem in Excel. I go to save a file that I
recently opened and updated, and I get an error message that access to the
file is denied for a file sharing error. If I save the file to another file
name, and then immediately "save as" back to the original name, it works
fine. I tried uninstalling and reloading Excel (a very laborious process
because I must uninstall and reinstall all of Office Pro, and then download
all updates since my CD copy). This seems to fix the problem for a while,
but it returns a few weeks later. I am baffled. I am running Windows XP
SP3 with Office 2007 Pro. Any suggestions?