My Intel iMac (2.4) has invalid sibling links even after completely formatting. I have managed to get Leopard installed, but it is constantly beech balling and generally acting unstable. It started off with refusing to boot and under the 'alt' boot menu it showed the Mac partition as 'EFI Boot'. I tryed to repair this using fsck and disk utility but to no avail. I formatted the system and tried to install Snow Leopard, but the installation failed several times, each time at different points. I managed to get Leopard (10.5) installed. HOWEVER, if I run disk utility, I still get invalid sibling links and as I said earlier, it keeps beach-balling and probably won't continue working. I have run some memory tests and it passed all of the tests with flying colours. I'm just left wondering what else could be causing these problems. Thank you. Edit: I also have a 25gb Boot Camp partition at the end of the disk which is working 100% fine.