100 DPI fonts == BAD
I've seen this problem before.
Basically, the 'nvidia' driver runs xf86 in 100DPI mode, instead of 75DPI mode.
What you need to do is comment out all instances of the 100DPI fonts in your "/etc/X11/XF86Config-4" configuration file.
The lines will look something like the following:
Just fire a '#' in front to comment them out.
Also, if you're running a font server ('xfs' or 'xfs-ttf') modify the "/etc/X11/fs/config" file and remove the 100dpi stuff there too ..