If you have these effects in safe mode just after switching on the computer, then it is not related to heat, neither refresh rate, nor drivers.
Try to switch on the computer with the monitor turned off (may be some dangerous voltage is comming from the monitor to the card by the vga connector). Keep the monitor switched off several minutes, turn it on and see if the effect was already present, if not, then the problem may be in your monitor.
If it is incorrect AGP voltage, you may change it (+- 0.1v) from the bios and see what happens. If it doesnt work, try to unplug and plug the card, be sure it is perfectly perpendicular to the mainboard to ensure the best possible contact with he AGP slot.