I was trying to  extrude a 2 point line from the end of a flat square plain.
Trying it a few times it did not reckognize the new line depth when I tried to pull it down along the y axis.

Then received unrecoverable error
-2147417848

After trying several times without compatability mode
I then switched to compatabilty mode...

It now reckognizes the extrusion with depth and the outer most line can be picked and lowered along the y axis

Gforce 4, P4, 256Meg ram, win98