TRY THIS
My Zune reboots randomly also, and i have read all or most of the scenarios in which they happen. I think i may have a fix. Most of the restarts happen during high friction situations, (example: sitting at computer, sliding in and out of a car, so on). Some people think it might be due to their "third party headphones", I am 99.9% sure that headphones are not the cause. All headphones are generically built the same. But i have heard that the Zune has alot of safety circuitry built into it so that it shuts down when it receives a bad electrical input (like a power surge, a short, or something not normal). Other than the headphone jack, there is only one other outlet for electrical input, the sync port. I have covered mine with ESD (electro-static discharge) tape and used it without any more reboots, it could be helping or it could be coincidence. If covering the sync port with a non-conductive material yields positive results, then Microsoft should manufacture little rubber caps to put into the connector when not in use. That's all i got. try it out, let me know what you get.
Brown 30 in ToughSkin (home)
Blue 30 in ZuneTank (work)
Red 8 in leather fold (wife's)
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