http://forums.technicpack.net/threads/it-wont-load-any-of-the-games-on-the-technic-pack.55545/
http://forums.technicpack.net/threads/no-modpacks-will-launch.55498/
And this thread, obviously, at the very least. I'm willing to wager that with more input from the guy with the post about pixelmon not loading for his pack, probably can't get past the launcher either, as the same thing happens for any new pack I try to download.
This is from the comments on the "#373 Stable' post, which is the same problem as above I'm willing to bet, even if it's for a launcher build from earlier this week.
Believe me, if this problem was as simple to fix as just looking junk up on the forums, then I wouldn't still be here. Not to mention the fact that, like, 90% of these threads go unanswered in the first place, which makes it seem like this whole forum is pointless.
If you can explain why it works for my roommate and other players but not for me and some others, then I'm all ears.
I have noticed, however, that most of my hangups occur at the 'version.json' stage and with extracting the wrappers. They get that far and go no further, regardless of whether or not it actually makes it to 100%. Java is running in the background and continues to chew up memory, but that's about as much activity as I've seen it have thus far.
Your guess is as good as mine.