You may have a "B step" 80386 CPU chip with the Erratum 17 problem. Check
out the disk in R11 c2 called NEWDX / B1STEP / DXFIX. In the B1STEP
directory is an explanation, detection program, and work-around for this
problem.
Note that the documentation incorrectly recommends that you load the
program in ACAD.LSP. Load it using ACAD.ADS instead (see the ADS manual
for details).