Currently Being ModeratedMar 20, 2013 12:35 PM (in response to tiborfrommiskolc)
Make sure that time and date are set correctly.
If the suggestions made in these articles do not help, contact Apple.
Currently Being ModeratedMar 21, 2013 11:23 AM (in response to tiborfrommiskolc)
Sorry that suggestions in the article did not help.
Now you mave to contact Apple or take the computer to the Apple store to have it checked out.
Before that try SMC reset.
Reset SMC. http://support.apple.com/kb/HT3964
Choose the method for:
"Resetting SMC on portables with a battery you should not remove on your own".