x11vnc choppy after upgrade to 12.04

hi all,

having some issues with x11vnc after upgrading to 12.04.3.

using clinets ultravnc and tightvnc - tried using 8 colour client settings but evrything is still extremely choppy.
it seems like whenever i dont move around the cursor the screen blanks out and it only displays when there is input. is this some sort of 'feature'?
it worked completely fine using default settings on 10.04. i have a nvidia graphics card and i read that there were some issues with the drivers. i am on nouveau right now.

any help appreciated.