On XW8400 workstations, static meshes will sporadically extrude random vertices into infinite space:
in the viewport:

In the Static mesh editor:

This issue is somewhat erratic, but seems to occur after lighting has been built. This issue is not 100% prevalent so it is hard to confirm the actual cause. However, since it is probably caused by the older 1500 FX Qaudro's in the XW8400 workstations, disabling height fog or lightmass should resolve the issue. To do so, follow the instructions in the following thread:
http://www.sfdm.scad.edu/intranet/students/forum/viewtopic.php?f=65&t=168