Runtime Error

We just released a new program. One of our clients using the software has come across the following error when attempting to use a function button.
Run-time error ‘-2147417848 (80010108)’:
Automation Error
The object invoked has disconnected from its clients.

The program is installed on Win2k and I have not been able to recreate the problem. I wonder if it’s an actuall error in the code or whether it has to do with the client’s set up instead?
Any ideas?