[tor-relays] [WARN] Your system clock just jumped 100 seconds forward; assuming established circuits no longer work.

[grarpamp]

Since you say it repeats you oppurtunity to check the
system clock first:
- configure tor to syslog
- send an ntpdate -q pool to syslog every 5min,
 remove when solved.
- send *.* to /var/log/all

and see what you find around where the date lines
start to slide or jump past each other. Graph it
with rrd/gnuplot if you want. epoch format helps there.
Your timekeeping is probably just broke somewhere,
ie: your system has bad clock drift and also can't sync
because there's a firewall blocking ntp, so off goes
your time. Check that first.
It's not your isp since you say you're using
ntpd against external debian pool and odds are
not someone stuffing you bogus timedata. Though
your ntp cli query may not be the same as the ntp
daemon query re: udp/tcp port they use, stateful
firewall timeout, etc... ie: somehow ntp blocked.
Or stale/unwriteable startup drift files on disk. If ntpdate
is set, then under ntpd running for 15min+,
if ntpq -np does not show one asterisk(*) in front
of one of the nonlocal peers, you're not synced.
And you'll be no luck until you are, fix that first.

Not likely to be Tor or kernel, but you can then next
- move the drive to another known good mobo/cpu box.
- do the kernel event logging thing
- bump tor's loglevel