look at the stickies at the top of the 8800 device forum... threads with links to the latest OS version for each model is in the sticky section of the forums.
There is no "official" release of 4.5 for the 8830. You will not find a link here for the OS. Your best bet would be to do a google search. I am running 4.5.0.101 on my 8830.
Be warned if you ever call VZW up for help, and they find out you installed a beta, they will automatically blame the OS on any problems that you are having.. this is why I am going to just wait it out..
1) Its pretty easy to go back to an old version of the OS without losing your data. You could switch back until you issues is fixed and then go back to the beta version again.
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"There is no reason anyone would want a computer in their home."
- Ken Olson, 1977
( And we now wear them! Blackberries are computers too! )