When booting up, the screen just turn black with no response, can't even see POST, no error beeps. The monitor little LED colour is green, and not orange.

However when i press the reset button, the system can fire up as usual. Oddly, this black screen only happen whenever I fire up the first time in the day. Subsequent restart/reset comp in the same day will not happen again. Also sometimes at the XP loading screen and the welcome screen, the graphics are all cracked up, but at desktop all become fine.

Does this spell trouble for my ati card? I must say that beside these weird happenings at the start of the day, I still can play games at good frames, and do my work for the rest of the day without any hiccups.

I'm using XP Pro, Samsung SyncMaster 955DF 19-inch monitor, Powercolor ATI radeon 9600 Pro (Bravo Edition), Catalyst 03.10, and 2D driver 6.14.10.6404. Direct X 9.0b

What happens if you turn the monitor on first?

Sounds like the video card is not initializing correctly. When you first turn on the computer, it may not be fully powered thus causing initialization problems.

As an experiment, try turning the PC on then pushing reset 1-2 seconds later to see if it will boot normally.

What happens if you turn the monitor on first?
My monitor is always on, so when I shut down my system, it will go to standby mode.

Sounds like the video card is not initializing correctly. When you first turn on the computer, it may not be fully powered thus causing initialization problems.
I'm using an Antec Truepower 480w, or did I miss out anything? As for resetting, it is still e same.

Oh just an update, I can see the POST actually, only till the part when the POST displays my SATA hdds, the windows xp pro loading screen fails to appear, thus black screen and basically freeze from there onwards, still no error beeps and monitor led is green. I have to wait for a while, reset and it will start to load. My system becomes like that only when I shutdown and fire up again. If I just reset/restart when my system is already up, it will boot as per normal.