Windows 2008 ADC & DC LDAP issue

Dear All,

We are facing windows 2008 DC & ADC problem. Per week it's coming this error. When ever this error come, then we restart once the server. After that it's working some days.

Below the error:

The directory schema is not accessible because:
An invalid directory pathname was passed
For this reason, the New menu may be inaccurate, and extension snap-ins may not work properly

Data from active directory users and computers is not available from doamin controller because:
The server is not operational.

Regards,

Santh