Two things... *228 is the actual number for Verizon. Call that and press 2 to update your roaming lists. That should help.
If that doesn't work, and updating the Host Routing tables doesn't work, then check to ensure your phone's network connections are set to 1XEV. Go to Options > Mobile Network and ensure that Network Technology is set to 1XEV.
OH you know what?.....I just thought of something...
The radio file in .148 might be messing with your device: just a thought though. Perhaps this same radio version incompatibility problem with verizon phones and .148 can be found elsewhere in the forum....
What made me think of this is your edit at the beginning: you get a data feed, it's just inconsistent.
I was having the same issue. VZA determined it was a phone issue. Difference is I was having it on any OS I tried, .75, .132, .148. Battery pulls, registering the phone, nothing worked.
Best way to troubleshoot would be go to a previous OS and see what happens.