NXT failure help

[FeartheGear]

Hello, I am from team 3567, Fear the Gear. At our last two competitions, we have experienced some technical issues with our NXT that have baffled us. During some matches, our NXT locks up and will no longer respond to any commands we give it. The field control system says that it is recieving input from our controllers and successfully relaying the input to our robot. Yet our robot stays completely still. After the match, when we try to push buttons on the NXT, there is no response and we have to take out and put back in the battery to get it to respond to buttons. We think that this problem might be caused by an impact to the robot. Sometimes this problem occurs when we have a hard contact with the ground after coming off a field element or being run into by another robot, but this is not always the case. Sometimes it occurs after a match, after Samantha has stopped the robot and it disconnects. We currently have only experienced this problem while using Samantha, but we are not sure if this is a concrete causation. We would really appreciate any input, thanks!