I had very similar issues with my Bionic losing ALL data signals (4G, 3G and 1x) and I finally found the reason behind it. When getting my Bionic, the first thing I did (besides rooting it of course) was to sign in with my Google account information and then start to restore all of my hundreds of apps from my Droid-X. Then I started losing my data signal and NOTHING would bring it back... not toggling wifi, airplane mode, bluetooth, even rebooting the phone didn't help. Talking to Verizon AND Motorola for over an hour didn't do any good since neither of them could fix the problem.
I then remembered what another Verizon technician told me a while back when having problems with my other Droids, and that was that "when upgrading to a new phone and having problems, DON'T RESTORE YOUR PERSONAL INFORMATION/PROFILE when signing into your Google account on your new phone" because many times this information gets corrupted and restoring your profile by checking that box basically restores the errors too (sorry but I forget the actual name of this check box but it refers to your personal info, private data, profile or similar wording).
Therefore, the only way I was able to get my data signal back was to unfortunately perform a "factory data reset" and NOT restore my private data, and I have had a strong data signal all day everyday since then (which was last week). I often switch from 3G to 4G and really never even drop down to 1x anymore. I have restored my apps and all is working great!
I know that it can be a hassle to reset your phone because you'll have to put all of your apps/games back, but you do however still get all of you contacts, calendar events and everything back even without restoring your "personal data" and it was the ONLY way I was able to get past the crazy data loss issue. One more thing, when resetting the phone DO NOT select "erase internal storage" because for me that just caused the phone to sit there and hang therefore doing NOTHING forever, so ignore that check box too.
I hope this info helps all who are having data signal issues since it surely cleared mines up and allowed me to enjoy the phone again.
Good Luck.