WHEN DRAWING A 3D SKETCH AND SELECTING TO DRAW A LINE, THEN BRINGING THE CURSOR BACK ONTO THE SKETCH THE IT LOOKS LIKE AN EXPLOSION. WHAT COULD BE CAUSING THIS?
That's difficult to diagnose without seeing what this "explosion" looks like.
It could be the graphics card (probably). Approved cards are listed at the SW web site. Comments on questionable cards are also listed. What card and system are you using?
I had (have) similar problems and it is really an graphic card issue. On my home PC i am using ordinary ATI gaming card. After 1 hour of working on complex assemblies it starts to scramble parts of screen etc. Just restart SW and go on.