I've read in a few threads that on beta OS 4.5 (1) people are having problems with google maps, and (2) AT&T people are having trouble with blackberry maps.

I have solutions to both problems. Tested on an 8820 running 4.5.0.18 and 4.5.0.27 and an 8310 running 4.5.0.37. Even thought Google Maps and BB Maps overlap to a large extent, I like to have both applications working on my device -- google maps has better search capability, bb maps can be set to track up
instead of north up, so it's better for navigating
1. Google Maps. The issue reported is that the application hangs after you give it permission to access the radio information. Eventually, the app times out, and it's never usable. I experienced this as well. The solution I found is to downgrade to 4.2.2, install and run google maps, make sure it works, and then upgrade to 4.5 and let BB manager back up all databases, etc. This carries the permissions over and will allow google maps to run.

If this doesn't work for you here are some OTA links for an older version of Google Maps that will work (no cell triangulation, though):