Hi ancient Mac user. The only viewer that works with OSX 10.6 is Singularity viewer from 2014 version Singularity_1_8_6_6156. . Download it seperately and do not login with Firestorm. Its good in medium settings. I use an iMac 24" from 2007 too with 4G RAM and the 256 Mb ATi videocard. Hope to survive SL in 2016 . The Mac will do it. Greetings Franklin Quar - Brown Mainland resident