as long as you see -- BEGIN RSA KEY & --- END RSA KEY at the end your 4G is in tact.
to backup your 4G keys use clockworkmod recovery 2.6.0.1 or amon ra recovery and perform a nandroid. Inside of the nandroid will be a wimax.img file, those are your 4G keys
I copied mine to my computer and emailed them to myself through gmail just so I'll always have them.