Well, the red screen problem at boot happened to my A2000 just
a few days ago, or so, and I've solved it be replacing the Denise chip. The red colour code indicated a rom checksum error, but in my case it wasn't the rom itself that caused it. I realized this only after replacing custom chips, one by one, and when I got to Denise, my red screen at boot problem dissapeared. ;-)
Too bad that A600 has surface mounted chips. :-(