Do you have an external preview device on using a firewire output? That was an issue in 9.0 which got fixed in 9.0a then brought back in 9.0b. If so try disabling the firewire preview and see if that fixes it. I realize that’s not the proper usage of the word “fixes” because if your car’s engine is broken you don’t “fix it” by not using it an taking the bus instead. That’s right Sony, that analogy was for you!
If it’s not the firewire preview then I have no idea, sorry.