>>What is the command you are using to close Excel
>
>I don't close it through a command. I keep it open, so that the user can see a report, which is sent to Excel via Automation. The error appears when the user closes Excel manually - and only if a single Excel report was produced.
>
>> and what exactly is the error message?
>
>I will have to check that when I am back at work. Something about Excel doing an invalid operation, and Windows having to close it.

What is your Excel version? I vaguelly recall seeing this problem discussed on another forum, but I think I need more information.

Is your application already closed at the time of error? Do you use form's reference to Excel object or just a local variable?