It may be that the card you're using pulls more power from the AGP slot than the board can supply. This isn't only a problem with Slot 1/Socket 7 motherboards; I helped a friend out with an AMD AM2 motherboard when I upgraded him to newer stuff, and he had me take the old parts and put that together as a backup. He had added a basic Nvidia video card on my advice because the onboard video was too old and underpowered, but that card went with the newer system. I had a pretty basic AMD PCIe card to use with the old AM2 motherboard, but it wouldn't turn on every time, and I finally realized that it was the video card because it would work with no issue when using the onboard video (even though that card worked perfectly in other motherboards). We picked up a used AMD HD something that had an eternal power connector, and that card worked perfectly with that motherboard.

There's a Newegg review that mentions this board is picky about video cards.

Those motherboards had problems with the caps especially in the cpu vrm area. Post a picture with your board.

All caps look fine.

If you remove the ram, do you get the missing ram beeps in the speaker every time (e.g. after a cold startup)?

Yes, every time. However, I think these boards just doesn't likes this ASUS gpu. I also have Radeons 9600 Pro, 9600, 9550, 9250, geforce 6600, FX5500 and none of these cards have this problem.

It is possible that the video card is drawing to much power, that's why i asked about how it behaves without ram.