Because there's nothing to fix?
First of all - relog.
Second of all - it's shitty L2's engine where you simple get stuck in invisible walls all the time when you don't relog for long enough, until the point when you can't move at all.
I won't even mention this massive FPS drop after 30min of farm in GC...
Hes propably talking about small rooms in GC. No relog will help you there. 50% of these rooms are bugged and you simply cant target the mobs there but when you get spoted mobs can attack you and there is nothing you can do about them. I wanted to go exp there last night but couldnt cause threre is nothing to hit :/ .