Game crashed while I was in dungeon in kaga or whatever that map is called. The error code would be ERR 00101. I tried to log back in and it let me go to character selection and got the same thing even with a different character.

It happens. You might wanna re-install or something if it's constantly happening (if you suspect its coming from your end). Otherwise just give it a few days or something. It happened to me for a bit.

What was the lag situation like? You may have been booted by lag, in which case log on when it's quiet (8pm EST seems to be lagpocalypse, so either log in well before then, or from around 9-9:30 onwards). Aside from that, I can only think of updating drivers, or else reinstalling.

The only crashes I've ever experienced were lag related, barring that time when Repairing Benkei was bugged.