Odd cell behavior: formula replaced with formula value

I have a spreadsheet that has begun behaving badly.

The behavior: Certain cells are supposed to hold formulas, but upon recalculation, the formula is often replaced with the value of the formula.

The affected cells are ones that at one time contained custom functions. Other than that, the behavior seems random; it doesn't happen every time the sheet is recalculated.

A formula copied into the affected cell often transmogrifies into the formula's value on its own. I can sometimes get around this behavior by dragging & dropping a formula from another cell, but the bad behavior eventually will come back.

The worksheet has been copied & recopied repeatedly; I am not certain if I could avoid this type of behavior if I made a template.

Any idea what could be causing this kind of instability? I'm running Office 2003.

Thanks for any ideas & suggestions.

Mayo99

I have not heard of this type of problem before. Certainly I have heard of formulas showing the formula instead of the value. You mention custom functions, but these UDFs would just show a NAME! error if they no longer existed.

I am suspicious of the repeated copying of sheets as this certainly was an issue in early releases of 2000 but not 2003.

I can only suggest 3 things, unless someone else comes up with anything

1. Ensure you are completely patched up to the current level
2. Try re-building a version of the worksheet to see if it goes away
3. Attach it here and let us take a look and see if it duplicates here