[c-nsp] weird hardware failure, looking for wisdom

[Joe Pruett]

my 7206vxr with npe-g1 started whining about voltage levels today. i
didn't want to have it fail over the weekend so i did a full power
down/up and it didn't come up at all. started swapping parts around and
if i slap in an old npe-400, it boots but still whines about voltage.
swap the i/o card from one with the single 100mb port to one with just
console and now it isn't whining anymore.

is it likely that something blew the npe-g1 and i/o card? or could i
have a backplane problem? i have dual power supplies and it doesn't seem
to matter what combo of those i use. i think i even tried another supply.

what gremlins am i dealing with?