Exchange 2010 error

this was working fine and then i cant mount the DB

Log Name:      Application
Source:        MSExchange ADAccess
Date:          5/13/2011 7:34:44 PM
Event ID:      2114
Task Category: Topology
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      eff
Description:
Process STORE.EXE (PID=7544). Topology discovery failed, error 0x80040a02 (DSC_E_NO_SUITABLE_CDC). Look up the Lightweight Directory Access Protocol (LDAP) error code specified in the event description. To do this, use Microsoft Knowledge Base article 218185, "Microsoft LDAP Error Codes." Use the information in that article to learn more about the cause and resolution to this error. Use the Ping or PathPing command-line tools to test network connectivity to local domain controllers.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange ADAccess" />
    <EventID Qualifiers="49156">2114</EventID>
    <Level>2</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2011-05-13T23:34:44.000000000Z" />
    <EventRecordID>8104</EventRecordID>
    <Channel>Application</Channel>
    <Computer>BDCVA.tmgva1.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>STORE.EXE</Data>
    <Data>7544</Data>
    <Data>80040a02</Data>
    <Data>DSC_E_NO_SUITABLE_CDC</Data>
  </EventData>
</Event>Topology discovery failed, error 0x80040a02 (DSC_E_NO_SUITABLE_CDC). Look up the Lightweight Directory Access Protocol (LDAP) error code specified in the event description. To do this, use Microsoft Knowledge Base article 218185, "Microsoft LDAP Error Codes." Use the information in that article to learn more about the cause and resolution to this error. Use the Ping or PathPing command-line tools to test network connectivity to local domain controllers.
Event Xm