My wife's 2 year old Toshiba L300 laptop has started exhibiting a nasty screen problem. From start up (ie switch on and BIOS splash) the screen goes into a peculiar cycle: every 3 seconds (or very close about) the screen garbles with fine horizontal lines across the screen; it then becomes normal for a similar length of time and then garbles again. The brightness of the screen is unaffected so I doubt it is the inverter. Attaching an external screen is normal. Help!!