Right, well, if you have a nandroid backup of a ROM where 4g worked, and you used RA (and chose the option backup wimax) or Clockwork (2.6.0.1 or up), then you can restore that nandroid backup. If you've lost 4g for good, though, as detailed above, and don't have a nandroid backup that includes your wimax keys, then you'd need to bring your phone in. I assume that is the case you are asking about. In that case, you'd need to unroot. There are instructions in the Rooting for Dummies sticky under the After Rooting section. If you rooted with unrevoked, you need to flash the S-ON tool to change S-OFF to S-ON. From there, you *could* run a RUU from your computer, but the preferred method is to use a PC36IMG.zip file. It's just a file you flash from hboot that is used to flash img files to whatever partition you want. In this case, the PC36IMG.zip file must contain all the img file contents of a full RUU. It will basically fully unroot your phone (once you have S-ON already, of course).