Cell style increasing spreadsheet size

[ExcelDave]

I have a big problem in my hands with Excel 2007. All of the sudden many
Excel Files has shown problems with Cell styles. Each time that the user
copy and paste, it creates a new cell style. We got to the point that we
couldn't even save the file without losing the changes made to it.

MY QUESTION:

Is there a way to delete all the cell styles at once? Our work around is to
copy and past special Unicode text or past as XML format, but is there a way
to eliminates the cells styles all at once? There are more than 4000 cell
styles...

Thanks for any help!