OABGen encountered error 80040115

I am having some issues on OAB Generation

The error logged in Event Viewer is below.

Event ID: 9334
Source: MSExchangeSA
OABGen encountered error 80040115 while initializing the offline address book generation  process. No offline address books have been generated. Check the event log for more information.
- \Default Offline Address List

Event ID : 9330
Source: MSExchangeSA

OABGen encountered error 80040115 (internal ID 50004b0) accessing Active Directory DCSS2 for ''.
- \Default Offline Address List

My Envoirment Details:

Root Domain is : Root.Local
Chiled Domain is : MyDom.xyz.com (Used new name tree option Windows 2008 R2 ADS) - Exchange Server Installed here, version Exchange 2010 SP1 RU3v3.

Root Domain got 2 DC/GC : DCS1 and DCS2
Chiled Domain have 4 DC/GC: DCA1, DCA2, DCB1, DCB2

Can you please advice???

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Thanks, Sandheep