There is some incompatibility between vncviewer and some local applications with regard to PRIMARY. I've tested xterm and emacs on my Fedora 19 and vncviewer doesn't pick up PRIMARY from either of them. There has also been reports on tigervnc-users that konsole and gvim also have problems.
Fixed in r27838.
Tested using tlclient build 4109,
Verified that PRIMARY clipboard worked from gvim / xterm and emacs.