P4R800-VM won't POST until reset button pressed.

I've had this board for awhile now and have had this problem from day
one. Have upgraded to latest BIOS, but didn't help. Have tried many
different things found on the WEB, but nothing seems to help. When I
first turn computer on, it does not POST and no beep. Fans, HD,
Monitor, CD lights all come on but no POST, no beep. Once I press the
reset button, system will POST, there is a beep, monittor light turns
from yellow to green, then starts normally. If I do a restart after
it's been on, it's OK. If I do a complete shutdown for a moment, it's
OK. Once it's been off for while, several minutes, hours, or
overnight, it won't POST until the reset button is pressed. I haven't
worried about it much, since it starts everytime after pressing the
reset button. I e-mailed ASUS support and they told me the power
button was probably bad. Since everything turns on when button is
pressed, I decided not to e-mail them back. Has anyone else had this
problem with this board? Please post here.

RG