Hi, I've got problems with ATi 3850 too. When i'm working with models with a bit higher poly count i encounter one or few seconds lag, depending of the model complexity. For example: when i want to orbit camera around model, the operatoin will not start right away. It wil pass few sec. and then camera starts to orbit around model. It's same when i want to do any other action on model. I installed latest ATi Catalyst drivers. My config is Athlon64 x2 2.7GHz, 2 gigabytes of ram and Win XP SP2.

I didn't have this problems with my previous ATi 9600xt card. Same sketchup 3dmodels now and then.