I would be totally shocked if the SCSI controller replacement fixed it in any way, but the bournes filter is suspect, in my book...

I want to add that I have only ever seen the "strange artifacts" on a cold-boot; once an OS has been loaded and restarted, they have never occured.

They seem to occur less often now that I replaced the PRAM battery, too. I don't know if this is related or not.