Problem with custom styles

Hi,
I have the weirdest problem. I am working with Excel 2007 and suddenly found one of my files wouldn't open in Excel 2003 saying that there were 'Too many cell formats'. I go back to my file and see that I have hundreds of custom styles all named in the following fashion
Normal x y, where x,y are numbers.
Upon trying to delete any of them, a new one is created with the next available number. For example, if I were to remove Normal 12 13, a Normal 12 14 would appear. I am not sure how to remove all of those custom styles (that I never created). Any help will be appreciated.
Thank you!