Takeshi,
I removed most of lines from my vgainit.inc (which was originally posted by Andrew Ip, and I modified), as far as VGA is enabled, and the problem disappeared! Registers 0xf8 and 0xf9 are not necessory either (so, only 0xfb is the one to enable VGA), but it might be safe to leave them. Below is my current version of src/northbridge/via/vt8601/vgainit.inc.
Have you got vga working on EPIA??? Does it have to be with ADLO?
-Andrew