It sounds like one of your mods is causing this, I would suggest uninstalling a single mod at a time until you find the issue. You could also list the mods you have here or post the whole error you are receiving.
Considering that this is a father posting this, I really don't think he would have a clue what a mod is. Probably firewall blocking java or something important. Besides, when is the game actually crashing? In LAN? Just before the title? We need more information than that. Plus this should be in the support area.
Rollback Post to RevisionRollBack
To all of you people who think Notch is still working on the game, he stopped working on Minecraft in late 2011. Get your facts straight and stop spamming his twitter about Minecraft updates.
Help ! been on for 3 hrs tryin to get it to work for my son. server tick