OK, I updated to Win 7.5, and then lost my 3G. I restored back to 7.0 and have the 3G back.
Now, somewhere I read that unistalling the HTC Connection Manager App and then re-installing Win7.5 will do the job.
What is the "HTC Connection Manager App"?
Klatu2691, I'm glad you were able to get your 3G back, but sorry to hear you had to lose Mango to get it working. What we have seen from some testing is that an application called Connection Setup downloaded thru HTC Hub is causing this. Have you downloaded this application or something similar? If so, you can uninstall that application. Otherwise, a hard reset should also resolve this issue. You will need to make sure your data is backed up since this will erase all data from the phone and reset to factory settings.
If your using your phone on Verizon and Verizon only, do not download and change any setting via that app. It is of no use to you unless you are traveling internationally and may need to setup a GSM connection manually.