The weirdest thing ever.

[Radical Pi]

Probably a coincidence with it being on the field only, but I've seen this problem before. It's a problem with the camera and the WPI code. If the camera hasn't finished initializing, the console is flooded with errors until the camera finishes loading (ring turns green). The flooding slows down the rest of the system enough that watchdogs trip and halt the robot intermittently.

If you wait for the ring around the camera to be green before enabling the bot (and an image is showing on the DS if you have it referencing the camera in robot init), there shouldn't be any freezing