I have had the SAME problems with the snapshots and the 2.x release ….its very random.
it is not a switch issue, wire issue, and the only thing i can think of is a driver problem, but that said....i have tried four different NIC card makers and all of them have the same issue.
link to my original post aboot this issue: http://forum.pfsense.org/index.php/topic,40147.msg207235.html#msg207235
strangely enough the link does NOT stay down …its what i call a hiccup that isnt even noticed unless i do a constant ping for days upon days.