Problem modeling my character

[Anonymous]

So I'm trying to create a small mouth for my dragon. I already created the bottom, but when I try to do a symmetry w/the bottom jaw, the thing just crashes.
I took a scrnshot and even Merged said character into a new file, but that does nothing.
What you see is me trying to move the jaws by selecting the vertices and moving them away. When I don't grab all vertices, I try to undo the move and then you see the error message.

I need help fast. Please.

[Anonymous]

I find that message a pain in the butt i must have message about 50 times every time it comes i fill it out and sent it off to autodesk and they never reply. and that message is no help to you at all lol

[Steve_Curley]

Post the scene please (zipped). Lets find out whether it's the model or your system which has the problem.