Graphics lag relates to the lag caused by moving around the game, time taken to load up polygons and whatnot (eg. landscapes, characters, monsters, buildings, etc).

UI lag is the lag caused by using the menu and the various things you can access from the menu (eg. inventory, selling and buying items, crafting, etc).

Regarding crashing - yeah, I've crashed about once per day over the past five or so days (averaging about 4-5 hours per day when you consider there was a weekend thrown in there) - hopefully these things will get less and less frequent (it's already a significant improvement on when Open Beta began!) as they learn about various problems and resolve them. Such is the kind of thing the beta testing was always going to experience, what with so many different hardware setups out there in the PC world.

Crashing is fairly mild annoyance for me normally, but when you're in the middle of a leve (which takes 48 hours to recharge) and you crash and it causes the leve to be considered as "abandoned" regardless of whether or not you log back in immediately - now that's just frustrating! Looking forward to them fixing that. Hopefully they do!