1) Edit your /etc/inittab file and change the line with "id:5:initdefault:". Change the 5 to 3 so you have to type the "startx" command.
2) when you type startx you can specify a log level to increase the verbosity of the messages. I think the default is "5". Above that you get more info. Try something like:
startx -- -verbose 6 -loglevel 6 (you need the -- )
The verbose output goes to your screen, loglevel to the logfile.
3) Check the log, I think it's /var/log/XFree86.?.log
You need to verify what file is being used as the XF86Config file, and then mod the settings for your driver.