Inspiron 9300 - Blank display after start-up

For some time now I've been having issues with my display on my Inspiron 9300.  I'd be in the middle of doing something and the screen would just blank out.  The problem would usually go away when I closed the lid and re-opened it, though sometimes that doesn't work and it just stays blank.   Recently though nothing helps.  I can restart it as many times as I want, but as soon as the initial computer start-up and windows start-up sequence finish, it just goes blank.  I can plug into an external monitor and everything is fine.  Sometimes when plugged into an external monitor after about 30-45 minutes, the laptop display will start working as an extension of the desktop.  Any help offered would be greatly appreciated.