How do I regain control of my Vim session when it hangs while saving a file via netrw?

Question

I edit a lot of files using netrw in gvim. Sometimes, when I mash C-s to save, it will hang my vim session. I'm not sure if this is because of a network error, or because I also sometimes hit C-z at about the same time and do something bad to the child process, like sending it a pause signal. After I do it, I can't seem to regain control of my session: mashing various combinations of Esc, C-c, C-q, Pause/Break, and so on don't seem to do anything.

I can hit "X" on the gvim window and get a prompt to save my unsaved work, so vim is still working, but I can't change tabs or use any of the gvim GUI or issue any normal mode commands. pstree looks like this:

        |         |-gvim-+-bash---sftp---ssh
        |         |      `-3*[{gvim}]

Is there something I can do in Vim to abort whatever netrw script is running and get my command prompt back? Is it really hitting C-z at the wrong time that causes this, or is it something else? Is there something I can do at the system level, like killall -9 sftp, that will make vim start listening to me again?

Is there something I can do to prevent this from happening in the future?