Here's a couple solutions:

1) Go to settings>wireless>mobile networks >access point names. Look and see if an option called "Simple" is ticked. If it is, tick your network name instead of Simple. For example, for me, I have T-Mobile; so I have T-Mo ticked and not Simple.

2) Try flashing a new radio or ROM. I highly doubt this is your problem but it is worth a try. Try the .08 version radio or the .12, whichever you don't have.

3) Go to your carrier's store and see if you can get a replacement SIM card. I did this once and they gave me one for free. Just say you are having connection problems and you think your SIM is cutting out. My N1 once fried a SIM card. Just re-read post and seen that you did this. I would highly suggest you try my first option as I had a very similar problem and solved it that way.

Originally Posted by Closed Source Project

Here's a couple solutions:

1) Go to settings>wireless>mobile networks >access point names. Look and see if an option called "Simple" is ticked. If it is, tick your network name instead of Simple. For example, for me, I have T-Mobile; so I have T-Mo ticked and not Simple.

2) Try flashing a new radio or ROM. I highly doubt this is your problem but it is worth a try. Try the .08 version radio or the .12, whichever you don't have.

3) Go to your carrier's store and see if you can get a replacement SIM card. I did this once and they gave me one for free. Just say you are having connection problems and you think your SIM is cutting out. My N1 once fried a SIM card. Just re-read post and seen that you did this. I would highly suggest you try my first option as I had a very similar problem and solved it that way.

SORRY IM HAPPY CAUSE THIS DOES WORK EVERYTIME DANG T-MOBILE GET AT&T TOWERS btw HAPPY EASTER EVERYONE leave me a egg :P

I have tried MIUI ROM and latest Radio (5.12) for passed few days. The problem still remain.

The new radio giving more stable 3G connection many locations but lost 3G connection on the previous problematic locations.

Really not sure what to do with it now. I have tried everything that is known on the web.

Sent from my Nexus One using XDA

There's nothing you can do. It's between your phone and local base station.
You didn't listen to me earlier, I guess now you will.

It is sad that nothing can be done. The phone should at least switch to 2G when 3G is not available, but my N1 stuck there causing me loosing voice and SMS capabilities. This is fundamentally wrong on the phone.

Sent from my Transformer TF101 using XDA