You know what? Today the welcome screen appeared for just 0.5 seconds. It's there, but it seems that the time it's shown has ben dramatically reduced, as I can still access the BIOS/BOOT options through F2/F10.
I think that because of the monitor, sometimes CRT monitor have a slow refresh rate after restarting from beginning.
But the screen has been showing up for a long time, until I flashed the v0303 BIOS.
I have a TFT monitor, BTW.