Your post lacks valuable diagnostic information. You'll find a list on this page.
Lacking that information, yes: the upgrade to Lion could be the cause of your woes. You should know that for virtually any application that taxes a computer's resources, as the Adobe applications tend to do, you should avoid a simple upgrade and do a clean install to minimize trouble with them.
Here is a list of known issues concerning Lion:
thanks Dave-- will be more thorough in future--
Here's another thought: your machine may be trying to use QTX, which most charitably can be called, "a work in progress". It's typically referred to as "a dog".
If you don't have the latest version of QT 7 on the OS install disk, download it and get rid of that phony-baloney QTX.