This has happened 2 times so far. Once at ~100 miles before I ever took my JK offroad or drove her rough in any way, and once at around 1200 (I have an auto transmission):

I'd be driving on the freeway and find it won't switch out of 2nd gear. All that happens is my rpm's go up indefinitely and I have to pull over, shut off the engine, restart it, and it'll shift just fine all of a sudden (without giving it any break or anything - I shut her down and start her up immediately after).

Has this happened to anyone else on here? My guess is it's a computer problem...

 

Yes, some others have had the same thing. I believe it was a stuck valve in the transmission.

Could be lots of things.
Linkage out of adjustment
Stuck valve in the tranny
Computer glitch
Low fluid level (yeah, it's a fairly new Jeep, but you never know until you look)
etc.

I assume you have a new Rubicon.
Next time it does it, see if you can drive it to the dealer (if possible) so they can actually see what it's doing.