I found this too late!
I downloaded and installed PC Tools iantivirus yesterday. Firt off, I know Mac"s don't get viruses, but I got pulled in by the ads. Anyway, I ran the program and it froze about halfway into the scan. It locked my macbook up to where I had to do a hard power off with the power button. Now, my mac will not boot! I get the chime and the Apple logo, but no spinning wheel. After several minutes, the mac restarts and it goes through the same thing. It's an endless cycle! I emailed PC Tools and am waiting on a reply. I am running OSX 10.5.7. Bad part is that I updraded this a year or so ago off my brothers family pack. I don't have the 10.5 disk to use as a restore! I have ran the disk utility and everything shows ok. I'm at a loss on this one. Guess I'll have my brother send the disk or go out and purchase one for myself. I have learned my lesson!😕