This is what i did to fix my problems with vertical lines flashing on wake up using Inspiron 1501 with Vista installed on it. try to update bios first by going to support.dell.com found in drivers and downloads.. if not, go to device manager, click the plus sign next to display adapter, right-click the your display adapter and click update driver. it took a long time for the driver to update that i fell asleep waiting for it to finish. when i woke up, it prompted me to restart. After the restart, i tried setting my system to sleep. no more weird vertical lines flashing on wake up. checked device manager again, driver version is release date 6/2/08 ATI RADEON EXPRESS SERIES.

by the way, before these i tried uninstalling and reinstalling the video driver for ATI IGP Xpress 1150 either from dell's website or ati's. no effect. so try clicking on the update driver button instead.