I am a Support Tech for a company that has 16 Solid Works users and only 1 of them has this problem.  When they open a drawing and try to rotate it, it freezes and then jerks.  It does not give a fluid rotation.  Also, when he zooms into a area, part of the lines disappear.  When he zooms back out, the lines show back up.  Someone else can open the files and everything works perfectly.  We have replaced the Graphics card with another Quadro 2000, but the problem is still there.  He is using a Dell Precision T3400 with a Intel Core 2 Quad Q6700 and 8 gigs of Ram.  Any ideas?