My guess is this is due to all the updates to VR recently.
Unfortunately Fess, as much as I would like it to, your solution has never worked for me. I've alt tabbed and massaged TIR and AH endlessly and it still won't work. What kills is the only method of resurrecting it is to leave the game entirely, restart TIR (to be ultra certain) and then restart the game. This makes it a fun ender.
It has become so bad that I've been forced to also program view keys as a back up to the TIR system crash. If this happens 30 seconds into your flight or worse when you hit alt, you can either waste the whole sortie and start again which wastes your leisure time, or try to make something work. Going backward suddenly 5 years to what you used to use makes TIR not worth the investment in the game.
This would be all solved if there was a easy way to tell the game to reacquire TIR. I have had it happen just once but can't seem to replicate what made it do so.
Thanks!