I don't know how or when this happened, I just checked my stats after combat while switching some gear and I had negative crit chance.
This is on my monk, Mordakai. It does affect combat, outside of popping my Eagle Strike I wasn't getting any crits. It persists through zone changes. Logging out and in fixes it.
This is very problematic as a monk virtually subsists on getting crits.
I seem to remember another forum post, about an ability causing certain stats to go into negative numbers after a death had occurred while a buff was active? I had died during combat several times, it's possible I died with my Eagle Strike buff up and this affected it.
It seems to be a direct negative 50 to my crit, so it's possible the game is setting my crit back to normal levels, then taking the 50 from the buff off afterwards.