Graphic Bug

[Brori]

Over the past few weeks I've been getting a strange graphics bug. Basically the whole world disappears and anything my character is holding also disappears. Other player characters and NPC stay visible but also the items they are holding disappear. When the issue occurs the game becomes incredibly laggy but I can still move around the world, cast spells etc. Doing Alt+enter fixes the issue but it does sometimes come back, I found in sky for some reason it comes back more frequently when my chat box was updating.

Currently running a Radeon 6800 (non XT) with the latest drivers, anyone got any ideas?