There is no sticker on my friend's PSU.
400W recommendation is from the manufacturer as listed on the box.
Are these symptoms typical of weak PSU?
Ex.: You can see only part of the main character. No head or legs. Flashing bottom display.
What drivers are you using ? there is a known issue with that card in AGP flavour.
If you are not already using them try these. http://support.ati.com/ics/support/default.asp?deptID=894&task=knowledge&questionID=31542