I've had the same problem for some time, Really annoying.
Everybody telling me my XF86config-4 was wrong.
adding a line and modifying another isn't the problem!!
The driver just wouldn't start.
I am not an export. But what simply helped for me was to run drakconf
I changed the videodriver to a xfree86 3.x.x ( unsupported don't know what ) driver. saved, and changed back to an unlisted 4.x.x driver ( like vga or nv or whatever ).
I hitted ctrl+alt+backspace after saving and i finnaly saw that nice nvidia logo i wanted to see so long ago