Obviously it's very depressed. I suspect it doesn't like it's new
flatmate, a watchguard e750. I can only guess that it desperately
misses it's old x700 and in a state of protest it's shutting down it's
fast ethernet interface periodically until I return it's friend.

Ok cute story aside... Anyone every seen anything like this? No errors
that I can find, just about every 2 days or so, it will down the fast
ethernet interface since I upgraded the firebox. It's not a
speed/duplex issue (it was for a bit because I had forgotten I forced
the router.. crc's out the unmentionables, that would cause the
interface to drop every few hours).

WG asked me to put a switch between the two, but it's a remote office
and I can't get there at the moment. (5 hour drive each way)