Have you put set talk immediately before the offending line of code ? Check that you're not dividing by 0, this can cause unusual output. Check the actual calculation at the command window, see what happens.

If all else fails, the only solution is to place another grid on your form and gradually add the methods and events back in. At least you'll see exactly which method is causing this error. As you're performing a refresh, there must be something in this method that causes the XXXXXXXXXX. Put set step on before the line of code and trace the path. You sometimes find that code won't error when in set step mode, at least you'll know it's not that line of code.

Derek