Upgrading crystal 10 to 2008 getting a report application error. . .

We run crystal reports on a web server in the .net report viewer. We installed crystal 2008 dlls on our web server. I have a report with a cross tab that was originally built in cr10 that I converted to 2008 in the crystal 2008 application. This report runs perfect within the cr2008 app. But when I load it up in our .net report viewer I get a "Report application failed" error. This is only happening with our reports that have cross tabs in them. Any Ideas?