if you get cell signal at all, it should not be a radio issue.
i would try getting LTE switch from the market, and make sure you are on LTE only (if you are in a strong 4G area) if it doesn't switch, it may be a SIM issue.
if you can't get it working on CM7, i would try a sense ROM and see if that fixes it. if it does fix it, i would re-download CM7 again, wipe data, flash CM7 and see if that fixes it. it could have been a bad download.
if you have 4G on a sense rom, and not on CM7, you may want to try a different kernal...not really sure if that would help at all or not, but it may.