Just an addendum - the Diagnostics said that it reapired a problem.

I opened three Excel workbooks and when I closed each file I immediately got
the same error message. So instead of a 66% chance of it occurring, it is now
increased to 100%.

"Duane Nutley" wrote:

I have been playing with Excel 2007 at home and have noticed roughly two out
of every three time that when I close Excel, it brings up an error message
that Microsoft encountered a problem on close and needs to close.

(I just tried it again, and this time it brought up Office Diagnostics).

Is anyone else having this problem? It is not every time I close Excel, but
it is becoming more frequent.