When I try to press Control-Shift-<something>, only the <something> gets sent. To be more precise, it to happens with punctuation characters but not [a-z]. I saw another bug filed that seemed related about the shift modifier not working, but there was no resolution to it. Since you will probably want the same information as in that bug report, I am attaching an event log from xev; first just pressing '?', then Control-Shift-?. You can see in there that the control and shift KeyPress events happen, then KeyRelease's happen and so the bare '/' key comes through (which is what I see happen in my editor), then the modifier KeyPress events happen again, then KeyRelease's for everything. I tried this with Chicken-of-the-VNC and it works properly.