Sometimes Macs reserve bad surprises
I don't know what happened yet. I just rebooted a windows 2000 virtual machine in Parallels and finished installing recent apple updates, looked back and this was happening :-( PRAM and SMC resetted, Diag CD gives the same garbled-flickering effect... looks like I'm gonna have to bring it back :-( ... Lifespan for this one ~24h
iMac's bottom
Swapping the 512 with a 1024, added the 512 to the MBP