I believe you and I have the same setup and I have to agree w/fastie81. I saw a similar behavior originally. Even if my video (LCD, plasma, monitor, etc.) is receiving the input from the HDMI source and has the HDMI source as selected, just the fact that I had the VGA cable connected to the motherboard (VGA D-sub connector) would make the splash screen not show.
Test it out...just have the HDMI connector and no other video cables connected.