Any time I add duct or an mvpart in 2010 I get this error when I exit the command. It appears that the progam needs to cycle through the viewports when you exit the command and if any viewports are not visible on the screen you get this error, once per viewport.
This gets annoying when you are working on a tab with 5 or more viewports and you need to hit esc and wait 5 times each time you add a duct, couple this with the fact duct snaps are not separate from osnaps so you need to leave the add duct command each time you need to pull a duct from a diffuser.
I asked if I could get my old autocad back but they said no so if anyone can help me get rid of this cvport error I will be deeply indebted to you!
thanks!