we get Invalid text or object handle when using CrystalReportViewer control

we are running visual studio 2003 .net framework 1.1.

we have a web application that is using the CrystalReportViewer control.

That site has been moved into production. It is working for everyone except one person keeps getting this error message when he tries to generate a report:

Invalid text or object handle. {DAB9E175-89B3-4F32-820B-B921740EE710}.rpt

why would this happen to just one person and not anyone else?