Thank you for the reply, Peter.

The problem does not appear to be specific to any worksheet.
None of the sheets in my files have any code in their code modules.
There are no ActiveX controls on the sheets.
The problem is reproduceable on another computer with xl2003SP3.
I haven't tried Xl2007 yet. I don't know what to expect there.

What do you mean by CF and DV?

I have a collection of addins containing a great many macros. After a
sheet copy, some of the macros simply stop running before they are
finished, and many generate run time errors on different kinds of
statements.

One thing that always happens, is right after any the above problems
happens, excel becomes unstable. Can't select cells on a worksheet,
stuff like that. And then closing Excel triggers an outright crash.

I distribute my addins to a great many users, and I see this as a huge
problem.

Thanks,

Brian