how to force rhino to stop a command operation. cancel does not.
I suppose the short answer is that Cancel should stop any command.
You didn’t mention which command doesn’t behave nor which version of Rhino this is…
make 2d
show all
cut
split
the list goes on
I would suggest that you try this in the RH6 WIP - things like this won’t be changed for RH5.
When you find one that doesn’t behave in the WIP you’ll probably have to provide a detailed work-flow and/or file for debugging purposes.
ahhhh
well too late for this project
will try to switch, a little tentative to jump mid project, but why not…
but, is there something that I am not seeing in R5 that will help?
Probably not 
Save often and if things take more time than you are willing to use, kill the Rhino process…