I found out the hard way at my job that QTP 9.2 isn't supported on the version used with 9.1 and previous. Unfortunately, there isn't any documentation that points this out. I did manage to figure it out after several different tests.
Something else worthy of note: Since Hp bought the testing products from Mercury, support has seriously suffered. I was down for 5 days whilst we were trying to get our license server up and running correctly. It took calling our AE and threaten not to renew to get a response. Hp better watch out there are some darn good tools out there....IBM RFT comes to mind.