Use another Computer to load the OS from scratch.
If upgrading from another BB - do NOT bring anything over other than your bare essentials (Contacts, Tasks, Memos & Calendar). The problem is a conflict with an App or setting from your old files.
This is why I recommend using another PC other than the one you normally use to backup your device. I struggled with this problem for 3 weeks before stumbling upon the solution. I was reloading my OS sometimes twice daily - NOT FUN!! :irked:
Since I got things sorted, I have not had ONE unscheduled Boot or hung Boot.
The ONLY problem I have had with .450 is the darn Contacts bug has reared its head again. Although this time not as bad. I have all my contacts and can access them, but my other Apps (like Vlingo) can't - weird.
Good luck - hope this helps you out.