Nvidia's uninstaller doesn't seem to do too teriffic job when
it comes to remove existing (nvidia) drivers.
if your drivers seem to build fine without errors, but all you get is blank
X screen, try this :
drop to runlevel 3 and run Nvidia's installer with parameters '-a --uninstall'.
check out nvidia-installer.log that was created during uninstall and remove
'checksum mismatch' files it shows manually. most of these files have
driver version in their name (xxx.5536.so.1). if you find redundant files
left by earlier nvidia driver installs, remove those too.
don't remove files that .log reports as 'symlink failed, already exists..'