Hi,
Using the so-called 'open source' nv driver that ships with Xorg causes Wine at least on my hardware to misdetect libXrender as being buggy. This disables clientside font rendering and also causes the entire screen to go black whenever a Wine application has focus.
Just letting people know in case they see similar symptoms. I normally run with the binary nvidia driver which doesn't have the same problem, so I'll not be debugging this anytime soon.
thanks -mike