I just swapped my old 8100 BB Pearl for a new one (warranty issue due to gummed up tracking ball), and when I performed full "restore" function of my back-up data from yesterday, GMail application didn't get downloaded...

I downloaded the GMail from Google's site this AM, and found out that I am getting the same error message as many other users, e.g. "Network Unavailable, BlackBerry reconfiguration is required, etc...". Called T-Mobile, they said that they couldn't help (e.g. I should consult Google first).

While searching for the solution, I've read through this entire thread that has a lot of great information. Just wanted to share with everyone that one of the prevoius posts did the trick for me:

"...
this happened to me when I installed the new google talk. re-register.

Go to:
Options
Advanced
Host Routing Table
Click the scroll wheel and choose "Register Now"

Google talk worked after that.

Give it a try..."

I gave it a try, and re-registering the BB per instructions above worked ! Awesome, thanks for great help - this problem was really frustrating me earlier today, but now everything is working great.

P.S. More FYI: I had to do enterprise activation for our corporate e-mail, which has super-stringent IT-security settings that it writes on BB device. I performed "enterprise activation" before I downloaded the GMail v1.5.1 - maybe that was part of the problem...