Hi,
There are possible things to try:
1: The first is very obvious but have to tried to Regen or Regenall[/b] the drawing? If so, did it not take effect?
2: You may have accidentally have one of the shade commmands on. Sometimes you don't even notice because if you haven't any solids or regions in the drawing you can't tell but sometimes normal 2D entities may look rough. The only indication is how the UCS icon looks (normal flat icon for wireframe and coloured 3D icon for shaded).
Try turning off shade by doing View >> Shade >> 2D Wireframe and see if it works..
3: Open the Options dialog box (Tools >> Options) and click the Display tab. Check the values of the Arc and Circle Smoothness and the Segments in a Polyline Curve. By default, they should be 100 and 8 respectively..
Anyway, give them a try. Other that those suggestions, I'm not sure what could be effecting your drawing(s)..
Cheers,
Paul @ basepoint designz..
basepoint designz
renegade@tiscali.co.uk