When using Putty to remote into Linux machines this would happen to me ALL OF THE TIME. I'd be happily chugging along, editing some text in vi and my Windows instincts would kick in and I'd hit Ctr-S to save. Everything would freeze and I'd be sitting there wondering what in the hell had happened...

Apparently this is a fairly common problem. Take a look at: https://raam.org/2007/recovering-from-ctrls-in-putty/ The scrollbar should give some indication of how many "Thank You's" this article warranted!