Ever try to shut down your Mac and it simply restarts or freezes? Maybe you try to do the simplest things like run the Software Update in System Preferences or Repair Permissions in Apple’s Disk Utility and the program crashes. Ever try to install the recent version of OS X and the install program fails, even when booted from the CD/DVD? It’s not supposed to be this hard to work in OS X. Well, you’re right. In the land of the Impossibly Ideal, where you take a brand new Mac out of the box and never install a piece of software or peripheral, these things would probably never happen. But in our world of the Common Occurance, we add printers, scanners, cameras and software, software, software. You get the picture. And in this land, not everyone plays nice together. Granted, they play nicer than in OS 9, but there is still the occasional squabble. That’s when you have to come in and mediate.
First, when doing anything related to the OS, make sure to avoid any conflicts by turning off or unplugging everything not Apple. In the case of SCSI devices via the Adaptec 2906 PCI card or similar products, unplug the SCSI cable from the back of the computer. Even some third party USB devices like card readers, scanners and the like, might interfere with the normal operation of your system. Most of the time, powering them off should work, but when the device is powered by the USB or FireWire port, you may need to disconnect it. Second, make sure that all of your devices have the latest drivers. This often solves many of the conflicts that occur.
I have had one client that suffered both these problems. One was a USB 2.0 memory card reader, that when plugged in, would not allow the system to shut down. It would simply reboot. The other problem was with the Adaptec 2906. I could not upgrade the system from 10.3.x to 10.4.x (Jaguar to Tiger) without disconnecting the SCSI cable. Couldn’t run off the Tiger DVD, couldn’t Repair Permissions, couldn’t run Software Update. Very strange, you wouldn’t think that the card would have anything to do with it. But remove the cable and voila! everything worked.
Moral of the story: Beware everything. Even the most unlikely of suspects may be the one giving you trouble. And when it comes time to upgrade your OS to the next version, remove those pesky peripherals first.