So as an experiment I decided to force a time sync by changing my Windows time (not CMOS time) about 20 minutes ahead.

Instant 90002

I also checked my event log during my last 90002 and found a similar time sync entry. I think you might have nailed the cause of this particular issue. I'm not surprised I didn't think of it before, since it is absolutely insane that this would cause a problem. But after reading the other posts here I think I agree this is some kind of ultimate kludge solution to fix a speedhack that was common in FFXI (FFXI calculated character movement speed based on CPU clock speed for some ungodly reason).