Mac and the OS X are very stable and reliable. However, if you want
your Mac to work perfectly you have to maintain it properly. Most of
the errors and glitches that happen to your mac are caused by incorrect
permissions table. Mac OS X as a UNIX based system has a UNIX way of
handling the files. UNIX as a multi-user system has a special way of
manipulating file access. (More about file permissions you can read
here).
When the new software is installed on your Mac or you did some other
system tweaks, it's very likely that permissions will mess itself up so
you wont be able executing applications or it may happen that your mac
is acting weird. The easiest way of fixing permissions is by using Mac
OS X "Disk Utility" which can be found in /Applications/Utilities
folder.
Fixing permissions is recommended before and after installing any
software to your mac as well as installing any software updates. There
are various software available on the Internet to help you keep your
Mac maintained and in a "good health". Software such as Onyx or
Cocktail are doing a great job by not only repairing and verifying
permissions for you but also cleaning the internet
history,cache,temporary files and running optimization scripts.
If you for some reason are unable to boot your system,before you do
anything like re-installing the OS, try pressing command + S on the
system boot-up and it will get you into console mode. Type in
/sbin/fsck -fy and hit enter. Do that couple of times until it doesn't
say "System Modified". Before you use "fsck" command, I advise you to
open terminal, type in man fsck and read the manual page carefully. Not
all software errors are as easy to fix by using methods above. Some
errors and system misbehaving can indicate serious hardware failure so
if the problems persist, the best is to take your mac to an authorized
Apple service for a check-up.
