Sometimes (but not always) when I copy things from my Emacs X11 window and try to paste it into Putty, it hangs Putty. That's pretty annoying.
I can generally get out of the freeze by pressing Ctrl-uh-some-key-in-the-top-left-corner, but from then on paste doesn't work anymore.
According to the Putty web site, that's only semi-buggy behaviour. Well, I don't know.
But from the explanation on that page I thought I could write something that would grab what's in the clipboard and put it back, working around the problem.
Of course, that's general enough to have been done before, so now I use ClipboardFusion to scrub the clipboard contents, and it seems to work okay.
Actually, researching this blog post and re-reading the semi-bug web page again, I may have discovered another way. Isn't it ironic... *)
It also seems this may not be a problem if I start Emacs in one Putty terminal and don't use that terminal again for anything. That wouldn't be a problem for me, I have five other terminals open anyway, and I could always minimize the Emacs terminal to the tray. I might try that and see how that works out.
*) It is. If you subscribe to the Alanis Morissette school of irony.