Ahmed,
It's hard to tell the root cause to a problem such as this from the description alone. If the problem is reproducable, i would suggest pulling an information capture for the problem and opening a TAC case for analysis.
To pull an infocap:
Log in to the Administration Center.
Click Services > Logs > System Information Capture.
Enter or change the values on the System Information Capture Page.
Click Capture Logs.
Click OK.
Obtain the data by taking the following actions:
Navigate to the zip file specified on the page. The name of the zip file is based on the date and time parameters that you entered on the System Information Capture Page.
Click Export to File.
Thanks,
