Wedge, the next time your server has that error, run this in console:
echo(getSimTime());
then, a few seconds later, do it again.
if the time returned is the same time, your server... froze.
I've never seen any complaints about this in help, but it's happened to my server, pecons server, probably glass's server. I don't know what causes it, but I do know what they all have in common...