2007 converter “compatibility pack can not open’

I am getting that error on one of my users when he tries to open a 2007 Excel file with 2003. All of our users have the compatibility pack, but this is our first instance of this occurring.
I have uninstalled the application, fresh download from MS, then re install with admin rights. I am not having much luck in researching this error or finding a fix.
Thanks in advance!