You don't have any Parental Controls or such turned on?
Have you tried deleting the dock plist files?
To do so, click on the desktop to make it active, the go to the menu at the top of the screen and select Go then Go to Folder.
Type or copy and paste this in.
Then in the window that opens go to the Preferences folder and delete the following file. Before doing so, make a record of how you have your dock set up as it will reset it to the default.
Then drag your apps from the Applications folder and and any other folders back into the dock.
Instead of deleting the plist file, you can copy it to the desktop, and if this fix doesn't work, you can just put it back and your dock will be back as it was.
Thanks to you and to parna.
On the path to a cure I shut down the computer and waited until all settled then restarted the computer.
When the sign in window appeared I did so, but then held down the option key which eventually took me to the window of choices.
The amount of broadband allowance used to upgrade both computers and all the relevant applications required by Mountain Lion plus having to redo the upgrade of all the relevant application upgrades due to the AppStore 'timing out' saw over 17GB used,
This hampered (prevented) a reload of Mountain Lion.
I had already tried three (3) shut downs and restarts to no avail.
However, going back to the window showing choices, I chose to restart using OS X 10.8. This was a different way of achieving the restart,
Having said all of that, everything now appears to be as it ought to be, and I thank you for assisting with ways of overcoming the problem.
I am experiencing same problems.
Restart resolves this, but the problem keeps coming back.
Come on Apple, I thought better of you than break such an essential component of the OS !
I have to say, with each upgrade (Lion, Mountain Lion) I am experiencing problems that should have been ironed out years ago.
Why tamper with things that work well ?
I would love to see this solved - it is a frsutrating little issue. I can run the Killall command as suggested, and that works, but it is the equivalent to a one tiem refresh, something the OS does.
It does not seem like a wide spread issue. Does anybody else run any thiord party tools that may cause this? I run:
DockView - an addin that adds bade icons and preview windows
Default Folder X - An addin that provides more power to the save-as and Open dialogs.
Other than that - I do not see anything that could cause an issue.