Has anyone tried to upgrade from CR 6 to CR.Net???

I am using ASP.Net, CR.Net and Universe Database....If I create a report within CR.Net that works fine....If I create a report within CR 8.0 and then run it thru ASP.Net that works fine as well....

But we have most of our reports created in CR 6....and now that we have decided to move to web we do not want to create all the reports again. So what I did was opened up a report that was created in CR 6 in CR 8.5 designer....saved the report and then try to run it thru ASP.Net and it comes up with an error message

Failed to open a rowset.

can anyone please give me some suggestions on how to fix this error....

Thanks in advance.