Never had a problem like this before. 10.8.4 refuses to install, tried several restarts over several days. The strangest software I have is a Parallels virtual machine for Windows 7. It's just a plain old 27" iMac Mid 2010, 29.3 i7, 12 GB RAM, ATi HD 5750. Usually very reliable and a strong performer since 2010! I hate to be stupid, but I really can't figure this out. It's not like I *need* 10.8.4 instead of 10.8.3, of course, but I'm fearful that it's a sign of trouble ahead.