strange problem, sometimes when I reboot my dell 700m laptop I have a blank screen, nothing brings the video back until I plug a cable into the external monitor port and hook it up to an external monitor, then the laptop monitor starts working fine again, for a couple weeks, and it happens over again. I can reboot several times with no issues, then it crops up again. Really frustrating when on the road with no external monitor around to fix it. Any thoughts on the cause?