Thanks for reporting this bug, Burr.

It looks like this bug got introduced into the last beta when I changed face extrusion in order to solve a different bug, the one that was reported here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2999.1

That was meant to make a set of individual faces that are all on the same plane extrude in a common direction rather than each one going on its individual normal. But one piece of the change is kicking in for this case you show here when it isn't supposed to so I will fix that up.

- Michael