Question : i have this error code every couple minutes

Event Type:      Error
Event Source:      MSExchangeSA
Event Category:      RFR Interface
Event ID:      9074
Date:            03/30/08
Time:            10:23:09
User:            N/A
Computer:      MWZ-SBS
Description:
The Directory Service Referral interface failed to service a client request. RFRI is returning the error code:[0x3f0].

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Event Type:      Error
Event Source:      MSExchangeSA
Event Category:      RFR Interface
Event ID:      9143
Date:            03/30/08
Time:            10:23:09
User:            N/A
Computer:      MWZ-SBS
Description:
Referral Interface cannot contact any Global Catalog that supports the NSPI Service. Clients making RFR requests will fail to connect until a Global Catalog becomes available again. After a Domain Controller is promoted to a Global Catalog, it must be rebooted to support MAPI Clients.

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Answer : i have this error code every couple minutes

I recreated the key of this  "TCP/IP NetBIOS Helper "  servive  on the registry and it's OK now