Try ssh to the kindle, cd to kindlevncviewer dir and start the viewer manually by:
./kvncviewer.sh -password YOURPASSWORD 192.168.2.1:1
Maybe the log info can give you some hint on what's happening. You can then press Ctrl-C to disconnect/freeze, Up-arrow then enter to connect again.
It's easier to press than the Shift xx keys.
Or you can try the x11vnc server, which works on my case also. It is started in the Terminal, so again the log info can give you some hint on what's happening.
I can confirm that both Vine Server & x11vnc works on FW 2.5.8 (with usbNetwork 0.33N) and FW 3.2.1 (with usbNetwork 0.35N) on my DXG.