I might be a bit outdated here but I ma running the 8830 on Verizon with version 4.5.0.77.
Its been running smoothly for over a year now but over the past couple of weeks it seems to freeze up when I hit send on a text message.
Its not a permanent freeze, but it does take 5+ seconds now to send a text which is kind of annoying.
I have a 1GB card with barely and media on this device and, I am using BES.
I'd double that....do a batt pull to check to see if that works. ALso check with your provider to see if anyone else in your area is having the same issues
4.5.0.138 is the officially supported release. .75 was not. So if you had occasion to call Verizon Customer Support, it might matter. I went from 4.2.2.196 to 4.5.0.138, so I can't help you with the differences between .75 and .138. When I upgraded from 4.2 to .138, I lost the call timer display and the audio quality of Voice Notes in BBM went down sharply.