I was so excited to see this as I've been looking for a similar program for a long time, that was affordable. MacZOT offered it today for $50. So I tried it before buying and it's a good thing I did. I spent a half hour getting all my outside walls just right, right size, etc. and suddenly got the spinning beach ball. I'm running OS 10.4.10 on a 160GB iMac G5 with 2GB of RAM and I repaired permissions before and after installation so there's no excuse for the spinning ball. Of course, all my work was lost. I'm just glad I hadn't finished my project first!