Cells resetting to date format

I have a large (huge!) financial modeling spreadsheet that I use at work.  After upgrading to Excel 2007, I have noticed that cells appear to reset themselves to a date format at seemingly random times.   I suspect a bug in 2007--anyone else noticed this behavior?

Spence

The file format in XL2007 is completely changed so when they are converted the whole file is stripped and rebuilt and the new format is an xml text format internally.

This means that 'numbers' like 01-02 will be seen as dates during this conversion and will likely become 1-Feb in Europe, or 2-Jan in the US.

You may be able to stop this by pre-formatting these 'date looking' cells as text before converting the file.

 Thanks, but I was unclear.  The cells seem to *reset* to date format even after I have changed and saved the file.

sdl

I've seen it happen, but not just randomly without doing anything. We use 2007 at work (50 desks) and not seen that