Sorry for the late reply killer, you've been added. If you're still having problems with the modpack let me know, sounds like you're having a java issue but I don't know what would be causing it. I can teamviewer you later tonight or tomorrow if you've available.
Edit: I figured out what the problem is, custom Java garbage in the bat (I copied it from elsewhere), so works fine on my PC but doesn't translate to someone else's. I fixed it and forced it to run minecraft.exe, for a workaround rename minecraft.exe javaw, It will be fixed with the next release (MC1.3)
To manually fix: replace the "start javaw..." line in the bat with "start Minecraft.exe"