LT2002 could just not get rid of this problem once it showed up, and Autodesk never provided a permanent fix: some users had some luck turning off video card hardware acceleration but most of us never really found a fix. It was often, but not exclusively triggered by a Pan or Zoom function.
LT2004 required the Service Patch to be installed to remove the symptom/cause noted above. If you have done this or are using a version of LT higher than 2004 and you still get this problem, so far it's been solely attributed to a conflict on your PC with another software package, and often requires that software package to be removed or updated.
Current solutions can be found at these following links:
Gedit3 Topic Page