Restart the computer then immediately hold the Command key and the letter R key together until you see the Apple Logo. This will boot to the Recovery HD partition. When it boots you will see a window called Utilities, select the Disk Utility and then select Continue. Then in Disk Utility select Macintosh HD in the left column and then select Verify Disk on the right. If that is OK in green type then select Repair Permissions. If it is not ok let me know.
Hi Mike,Thanks - your help was spot on and I am up and running again.Two quick questions - 1) Does this happen a lot when people install OS X? 2) I will shortly be installing same on my laptop - if the same thing happens do I follow your cure?Once again, thank you very muchRegards,John