I also experienced the radio locking up. Nothing I did would get it out of the menu-couldn't even turn it off-required the removal of the battery for 10 seconds. The radio was NOT connected to the computer at the time. However, mine will turn on and function after replacing the battery. Provided I do not access the menu again. If I do, I'm back to removing the battery. The radio is stock except for the MARS/CAP mod.
I figure there is a software glitch or some type of improper manual programming I used that got me in this mess. I tried reloading my known good file with RT Systems programming software to reset it. It was then I noticed the radio was not getting programmed the way the software program should be programming it (or wants to program it). Bank linking was being ignored when scanning, allowing everything I had programmed to be scanned. (I have a bank I call NOAA WEATHER with the 162MHz freqs. It's not included in the linking but the radio scans and stops on my local NOAA freq.). Checking the radio's settings manually (no connection to the computer) shows that bank SHOULD be locked out. But it's not. I am further researching this issue.
My next steps are to first see if I can reprogram with Yeasu software. and then RT software. I want to see if either will correct. If not, move on to my next step which is to again attempt the same with both software packages after I check for and install any Firmware/Software updates that may be available. The results of these steps are attempts at isolating either software programming packages as the cause. If all fails, a hard reset, returning the radio to factory default settings and then reloading my known good file will be attempted. I will post these results here, hopefully later today.