What a day. I think Revit crashed about 10 times on me within 2 hours. It did not loke me to touch one particular wall that I wanted to shorten. The wall in question was joined to a perpendicular wall on the other side of the hallway, and I wanted to clear that way, because the fire-door I had previously placed here was no longer necessary.

I finally got around the regular crashes by first disallowing the joining (select wall > find the handle at the end of the wall > right click on that handle > select disallow join) of the two walls and then shortening the wall.

Phew. I do not want to be the one support guy reading all my e-mails I sent to Autodesk via the automatic crash report function...