I had the same problem and I found this solution on another thread in this forum. It worked for me! I have a mac so it could be possible that some of these things are named or located differently
1. Start TechnicLauncher
2. Top Right Corner (Launcher Options)
3. Activate "Increase PermGen Size"
4. Launch the game
If that doesn't work, I heard from a friend that the problem could be situated when you have multiple versions on java installed.
Hope it helps!