Graphics issues

So i've been getting disconnected often and I've come to the conclusion it must by a graphical issue.

My theory is that graphical lag seizes up my computer then the server boots me. It's really frustrating.

Currently i'm running in fullscreen 800x600 with shadows off, my FPS is fine most of the time, but occasionally i'll freeze and get d/ced. It happens most often going into the passive skill menu.

Are there any advanced techniques to solve this? I'm pretty computer savvy so i'm open to almost anything. (Other than upgrading hardware, if only because i'm poor. >.>)