We've been experiencing a problem of our NXTs locking up frequently.  Has anyone else experienced this?

We have several bricks and this happens on all the bricks, which I would think would indicate it isn't a hardware problem.  We haven't had this problem prior to this season.   Our firmware is up to date on all the bricks. We are using the 2.0 version that has the datalogging capability.

We know how to reset the NXT brick and  after we reset it, it is fine for a time.  We have to remove the NXT brick to do so... this would be terrible if it happened at the tournament... especially as the announcer says 3-2-1 LEGO!  

Any ideas of things to try? 
Cari N

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