Error in File ~tmp81c59e23760a10.rpt: Invalid argument for database

When trying to run the report via Crystal Reports Server, we get the following error:

Error in File ~tmp81c59e23760a10.rpt: Invalid argument for database.

Opening the report in Crystal Reports 2008 and running a verify database, confirms that everything is working. Yet when we run it through Crystal Reports Server it errors every time.

We are using a Progress ODBC driver which works fine when running reports via Crystal Reports 2008

Can you please shed some light on this.

I have already checked to see if there was a service pack or any other hot fixes available.