Media Encoder hangs on launch

Every time I try to launch Adobe Media Encoder CS5 (Version 5.0.1.0 64-bit), it hangs on the title graphic with the message:

"Loading ImporterQuickTime.bundle"

Left it to do its thing for 30 mins and it's still not responding.

Any idea what might be causing this problem?  I don't know what logs I should be posting.

FYI I'm running it on Mac 10.6.5 on an early 2008 quad Xeon Mac Pro.

Any help would be hugely appreciated.

Thank you.