I have verified your problem, it will not accept a direct entry of an LTR talkgroup ID as x-xx-xxx. This is the same on the PSR-400 and I'm sure it is on the Radio Shack Pro-163 and 164, since these radios are all the same. I have notified GRE about the problem via support. The good news is that the firmware is upgradeable, so lets see how long it takes them to correct the problem.
Have you been able to save an active talkgroup using "Ent"?