I saw this thread from quite a ways back on this topic :
http://forums.camerabits.com/index.php?topic=502.0
For what its worth, I am seeing occasional hangs on startup in version 4.5.1.1. The splash screen just hangs. It can be killed with the "force quit" option (didn't check the activitiy monitor). It always starts perfectly the next time. Has happened to me several times recently. Before (and after) I upped to 10.4.10 and after I took the latest update to PM.
Mac, non intel,G4 1.5 GHZ, 1GB RAM, other various apps running at times...
Hope that helps, let me know if any further info would be helpful.
Gregg