I don't have one of those fancy WJs, but to me it sounds like a bad battery, or bad connections on the battery. Happened to me on the ZJ, it was loose cable clamps. The alarm would go off (no horn just lights) and it wouldn't start. I would disable the alarm and get a jump and it would be fine for weeks.
I always thought I left a light on or something, until one day it happened in a parking lot, a guy was walking by and saw me fiddling with it and he said check the clamps. I'm like, yeah sure whatever (being a typical man) and I said, yeah I checked that. After he left I tightened them down and what do you know, hehe it worked.
Anyway, may apply to you, may not. It's worth checking out since it's a free fix to clean and re-clamp the battery connections.