If it fried those, I would think it might fry others groups of circuits as well. Though with that many cases occurring at once, you can probably rule out coincidence.

Not sure what happened, but I think it'd be cool to know for sure...

They might have been testing circuit-hardening methods, to protect their own circuits from being fried. In order to properly test it, they would have to generate an EMP far more powerful than anyone would be likely to use on the battlefield, and maybe it was powerful enough to escape whatever shielding they used to isolate the test area. (If, indeed, there is any shielding other than distance that would work.)

Actually, as I thought about it further, I can come up with a reason those circuits might fry - basically, they're very exposed (at least the input portion is), which could lead to the discrepancy between that and other items not failing.

also, need to take into account the inverse square law. Basically, forces like this tend to lose their power in a ratio that is inversely proportional to the square of their distance from the source. So, if the force that left the base was very powerful, by the time it got to Vegas, it was probably hugely less powerful (by several orders of magnitude), therefore, only sensitive exposed circuits were affected. Just a theory, but I'll sleep better because of it.