We'll need more information on your test and its error to properly troubleshoot. The "Export Result to File" feature in the Step Failure Details
dialog is a good start. If your test is against a public site, we can troubleshoot the quickest with a copy of the test (within a zip file) to see the issue first-hand.
All the best,
the Telerik team
Check out the Test Studio roadmap
to find out more about the new performance testing functionality coming in our R2 2011 release this September!
Have you looked at the new Online User Guide
for Telerik Test Studio?