Network died, what to look for?

Yesterday evening my Linode apparently went offline- no web access via name or ip address, no ssh access, no ping. I was able to access via lish, but couldn't quickly see any problems- Linode 512, standard LAMP stack, Debian Squeeze (an upgrade from a Lenny install). Plenty of memory, low load. A quick look at kern.log and auth.log said nothing, so…

I rebooted it, it came up fine, everything works, but I cannot figure out which log file to look at to see what exactly happened.