I have an iMac G5 20" that I purchased in Feb. of '05. In October, while running 10.3.9, I began to have issues with powersuppy which the apple store changed out for me under warrantee. Ever since then, I have had perpetual problems with permissions and directory structures. After numerous calls to Apple Care, one tech thought I might have a problem with a bad sector on the hard drive, so it was changed out. I was planning on upgrading to Tiger, so with the fresh drive, I loaded Tiger, iLife '06, etc. After running smoothly for one week, the permissions started failing eventually leading to loss of my host directory which prevented the mounting of the hard drive. Back to the Apple store. They perform diagnostics, restore my directory, and all is good? Wrong. After only two days, Icons appear like they are cut in half (like the little house in the finder) or are replaced by different icons, programs will open and quit unexpectedly, The Aqua interface will pixilate, but only on certain items. If this was a Windoze machine, I might expect this. But for the last 6 months, I have been dealing with this very odd behavior even with clean installs of 10.3 and 10.4. I say its hardware related (a bad power supply sending "just a little extra" juice?), but the Apple "genius" won't listen. Any ideas????