Macros are likely at fault. Let me explain.
Microsoft Office programs memorize your preferences. Your preferences are stored in a macro. Ever heard of the “normal.dot” file? There is a different .dot (document template) file for Excel.
Okay, so you have a problem with Excel’s document template file. What can you do?
1) Delete it directly. You can look up where to find the template file and delete it there. NOTE that Office 2007 uses .XML (extensible markup language) format files so their document templates may be .dotx (or something equally crazy).
2) Start Excel in safe mode. This loads without any macros. Exit Excel. This may flush an offending excel default document template. Exit Excel before opening anything.
3) Start Excel in ‘first run’ mode. Exit Excel before opening anything.
4) Alternate between 2 and 3 above until the default document template file is purged.
You may be forced to take a blank Excel default template from the source disk to replace your corrupt one.