One of the main reasons we bought a Mac was the 'ease of use' tagline that hooked us in, and yes, the Mac interface is very easy to learn and become comfortable with.
Sometimes it's too easy, and makes us too comfortable.
We are so used to things just 'happening' when we press the appropriate key, or ask the Mac to carry out a simple everyday task, that when things go awry we tend to reach for the panic (read Google) button.
I've just had a call from a good friend, and she has logged in this morning to carry out some software research at Cnet and Macupdate via her G4 Powerbook running OSX 10.
4.
11.
She downloaded three different apps, and they arrived, as normal, on her desktop, but when she came to mount them (i.
e.
double clicking on the.
dmg image) Safaris download box showed all three items attempting to load up, but after two minutes of sitting there spinning away she got the dreaded 'disk image failed to mount' error message.
A restart failed to cure the problem, and the.
dmg files were still there on her desktop.
As this was the first time this had ever happened she thought, as an ex Windows user, that she may have picked up a Virus somewhere (something that is virtually impossible on pre Intel Macs).
The problem isn't caused by a virus, but by simple software corruption that 'just happens'.
There are two ways to fix this problem, and it takes about 5 minutes of your time, and it also cures another Mac fault..
..
a sudden inability to burn CD's.
If at first something doesn't work as it used to - Repair Permissions! If you aren't running a maintenance application that runs all your necessary maintenance tasks in the background (like the easy to use - and free - Onyx) you will need to go to your Utilities folder that will be found inside your applications.
It won't hurt to repair permissions say once every three months, even if you can't see any problems manifesting themselves.
Okay, double click on the folder to open it, then locate Disk Utility and double click on that.
A Disk Utility window will open up, and you need to go into the box on the left, and select your hard drive by clicking once on it.
Ensure you select First Aid from the four button menubar (First aid, erase.
RAID, Restore) and press the Repair Disk Permissions.
Your Mac will now rebuild its permission list and it should take no more than 30 seconds to a minute.
When you get the Permissions Repair Complete message, I suggest that rather than coming straight out of Disk Utility, have a quick look at the Log your Mac has created up on the top right hand corner of the main DU menubar.
If it found a problem, it will most likely be shown there.
Now restart your Mac and try to open the dmg file again.
Nothing happens? Then you need to throw some files away...
Do the following things in this order:

• Open up a new finder window and click once on your Hard Drive icon
• Go to the System folder, open it, locate the Library folder and open that.
  
• Top of the list should be the 'Extensions.
  kextcache' file.
  Drag it to the trash.
  
• Now open up the Caches folder just underneath.
  
• Locate the com.
  Apple.
  kernelcaches folder and drag the complete folder to the trash.
  
• Go to trash and double check that the two items are in there.
  
• Empty trash and restart your Mac.
  

The Mac will rebuild these files as it restarts (it will take a little longer to boot up).
Once you are up and running, try those.
dmg files again.
Voila! Works for me every time.
Hope it works for you.