allright. installed the 4 simms into a spare cps3 board I had and started to install 3rd strike from SD2SCSI adaptor with the newest multi cd iso installed on the sd card.
Had a black screen after the region select screen. redid the whole process with a different game, black screen again.
Installed the simms into my cps3 board which I use almost every week, installed 3rd, black scren again.
I'm reinstalling again right now, but from scsi cd this time just to make sure it doesn't come from the adaptor or a faulty file which is on the card.
in 40min I'll let you know how it ended.
EDIT:
Installed the Game from the Cd ROm Drive itself and it worked right away.