Problem When Multiple Users Export To PDF Simultaneously

I am hoping someone out there can help. We have had no luck at all with Crystal Reports / SAP support for this issue.

We have a client/server aplication and have written a C# program to load a crystal report on the server, export it to PDF and then we send the PDF to the client. We are using Crystal Reports 2008 and have applied SP4.

The scenario is as follows:

Two users log into our application from different PC's.

User 1 prints a report with no issue.

User 2 prints a report 5 seconds later with no issue.

If User 1 prints a report and while that report is being exported to PDF, User 2 prints a report, the first will be successful and the second will fail. If User 2 reprints the report after receiving a failure, the report prints successfully the second time (using the same temp report folders as the previous attempt). We have done a lot of tracing and have narrowed the problem down to the point in out C# program when the cryRpt.Export() routine is called. It seems to be what is failing and doesn't seem to be able to run 2 exports simultaneously.

All exporting to PDF occurs on the application server and the processes run as "Administrator" so permissions should certainly not be a problem. Each user is printing a different physical .rpt file and the data for each report is in a different physical directory.

Has anyone come across this before or have any suggestions?