So, when my friend attempts to join, he can connect and all, but when he tries to enter the VAB or SPH, the game doesn't give him any parts to work with. Here's my log:

http://pastebin.com/J4A1zwns

and here's my Modcontrol

http://pastebin.com/ytGZLQ2D

Ask him to reinstall the game, it should work. If it's on Steam, verify the game cache. You can also try to copy the GameData/Squad/Parts folder from the most recent release and put it in your directory.

Unfortunately, we've already tried that. Would you like for us to try again and check the results?