Spreadsheet changed without my input...

[foxfoto]

I saved and closed 3 Excel spreadsheets I use constantly and when I reopended
them one had changed. Cell spacing was different, dates were represented as
serial numbers and none of the formulas were working and I cannot get the
numbers to show as currency like they were. I cannot change the formatting of
the cells and have tried repeatedly. I checked and the properties of the
program are not set to 'read only' and the cells are not set to be protected.
I am at a loss. I need this program back to the way it was and it is beyond
me. Seems like this happended once before too and I had a few day old backup
to revert to. Unfortunately I am running an external hard drive with auto
backup and it just copied this changed spreadsheet...

Any ideas?

Thanks!