Changed mb/cpu/ram, beeps are ok, leds ok, but screen in standby, help

My old (2005) configuration was, Enermax Silent 485W, a Gigabyte MB, Radeon X850 XT and Athlon 3200+. I bought an Asus P7P55D LE with an i5 760. Well, after upgrade i hear a beep after poweon, then i see they keyboard lights correctly blinking, then another beep and stop (which i think indicates that POST has finished), but no video at all. If i press ctrl-alt-canc system reboots correctly.

Ideas? I tried to:
- Swap memory, leave one bank and so on, nothing
- Removed power from the X850XT and motherboard starts beeping with the "no videocard" code
- Unplugged ALL disks, only motherboard and videocard are powered

Video card was working on the other mainboard.

Could it be the PSU?