Don’t let the Apple hype fool you, OS X will crash, break, screw up and infuriate you in just as many ways as Windows can. For example, the Software Update feature has taken to hanging recently - to the extent that I need to force quit it. I wasn’t that bothered as there weren’t any updates I felt I particularly needed, but recently Apple updated iTunes and Quicktime. Now, unless you upgrade to iTunes 6, you can’t buy anything from the store. But my machine won’t do the automatic updates.
No problem, thinks I, I’ll just download the iTunes package installer and run that instead. Bzzzzt. ‘fraid not. The image above shows the volumes OS X thinks it can install to. Now I’ve got three volumes - the 160Gb system disk, which has about 20Gb free, and two 1Tb storage disks for data. As you can see from the graphic it doesn’t think it can install anywhere - doesn’t even *see* the volumes. Gah!
I’ve given up for now and instead downloaded the tunes I wanted to buy from iTunes on my PC, which despite it’s many flaws has never had an installer fail to find a hard disc. Grrr argh.
MacOS X is much the same as any other OS in respect that it can be screwed up by a dodgy driver, poorly written software or whatever. I’ve certainly never had problems with software update, which is usually pretty reliable, with regards to the iTunes problem, it sounds like there is something screwy on your system drive (and this could possibly explain the software update hangs too). Apple installers will identify drives with particular characteristics depending on what is required. In the case of iTunes and the software update installs, your boot drive containing OS X.
As a first point of call try booting from your OS X install DVD, and starting up the disk utility, and then repair the drive permissions, from there you can also see if it is something more serious.