OK, I wanted to go to the leaked 2.2 ROM, so I did the following:
Un-root via PB31
Apply Baseband Update - to 2.05.00.06.11
Re Root/Re Flash
Everything works fine except that my reception is now terrible. Where it used to be good it's now bad, where it used to be bad it's now zero.
As I said in my other post, I can't unroot now, it says the PB31 file is too old (I think due to the baseband update)
Also, as I said in my first post for this thread, I've seen people talking about going back to a previous baseband version to fix similar situations (in the moto droid section) and I think that's what I need to do.
Follow the steps there. Its a great write up. Step 4 is the most important. You need to have the SDK setup cause this is the part where you will be tricking the PB31IMG that you have an older hboot and then it will run.
Here's a great video that worked for me. If you click "more info" under the video, he has a link to the files you need. I did this yesterday and it worked great. When I was done, I restored a nandroid backup and was on my way with the original baseband. Good luck.