Actually, this happens more often then "more often than not"... it ALWAYS happens.

That's what I originally thought, too--but I have actually seen Ctrl-Z start working with the parameter window active. I don't know how or why, but I was able to repeat its use several times. I'm guessing that the times it stops working or just never starts to work (i.e., most of the time) the window messages are getting lost in space.

Also, I have observed that even when Ctrl-Z, Ctrl-M, Ctrl-;, etc. don't work with the parameter window active, Ctrl-N always seems to work. Bizarre.

I note that clicking on the main Poser window and then typing Ctrl-Z to attempt to do undo a parameter dial setting has never worked for me.

Thanks for letting us know you've submitted the bug report; it saves me the trouble of distilling my frustrated rant down to professional language and sending it to CL for consideration. :-)