I've been looking at upgrading some tests from QTP 9.2 to QTP 11 with Quality Center 9.2.
One problem I was having was trying to execute tests remotely; I kept getting the "Class Not Registered" error in Quality Center. It turns out that you need you to install the QTP 11 QC Addin on both the machine you are launching the test on, AND the machine that you are running Quality Center from. Once the add-in was installed in both places (you can get this from the QC Help Menu and clicking through to the add-ins page) this error was resolved.....took me a while to figure it though!
