well... I'm having the same problem. I was upgrading to 4.5 from 4.2 and let it go like any other OS install/upgrade. Then.. it said it failed. Sucks... I'm sure i've lost ALL of my numbers.
I'm at a 507 screen, No OS... I load up desktop manager, it sees the blackberry but does not prompt to install the OS. When i click on Application loader, it see's my blackberry, ask for password to connect, I type my password but it times out and says it cannot connect...