Plot hole: Contrary to the realism of developing a video game Alex should have had external files such as character models, stage maps and coding on his laptop which he could have used as evidence that JP stole his game, It would be impossible to keep all of the games files on one disc especially if he wanted to change something in the game because if you want to modify a DVD-RW you have to erase the disc data and reburn it.
Continuity mistake: In the beginning of the movie, right after the boxing match on the Xbox, Alex goes into his kitchen to grab a drink. You can see Kevin Nash and another guy in the background. The other guy picks up a coffee maker and places it into a packing box. In the next shot, Alex asks the two guys what's going on, and in the shot after that, you can see the guy grabbing the same coffee maker from behind the box, and placing it into the box again.
Other mistake: During the Dance Dance Revolution challenge, the challenger should have won. Jeff does some outlandish freaky dance moves, which in no way correlate to the arrows that are on the arcade screen. The arrows that he hits, aren't even the same ones that register as being hit up on the screen.