Gah! No pastebin, please! It is horrid for cut and paste so I can't excerpt and point out things in your code here. There's a checkbox over the "submit" button that says "Disable HTML in this post"; check that and leave the code in there please.

It looks like the collision math itself is flawed. To me it seems you're just adding together the velocities of the collision balls withough any further computation. Are you using a specific formula?