File and Folder sharing stopped working Windows 2008 R2

Our network as a Win 2008 R2 machine. File/Folder shares have been working on this machine since we installed it. A few days ago, sharing just stopped.

If we use Explorer to view the server using it's UNC name (e.g. \servername) we can see icons for the shared folders. But when we try to access a share, we get one of two errors: [Window Title] Network Error

[Main Instruction] Windows cannot access \myserver\appsdata\BBookv3\data\0011250

[Content] Check the spelling of the name. Otherwise, there might be a problem with your network. To try to identify and resolve network problems, click Diagnose.

[Expanded Information] Error code: 0x80004005 Unspecified error

OR

[Window Title] Open Folder

[Content] \myserver\C is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions.

The specified network name is no longer available.

Has anyone seen this? I've seen other posts where people say that shares work if they use the ip address or FQDN. This is not our case. Nother we do gets shares to work.

    The following fatal alert was generated: 10. The internal error state is 1203.  - 

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
 <System>
  <Provider Name="Schannel" Guid="{1F678132-5938-4686-9FDC-C8FF68F15C85}" /> 
  <EventID>36888</EventID> 
  <Version>0</Version> 
  <Level>2</Level> 
  <Task>0</Task> 
  <Opcode>0</Opcode> 
  <Keywords>0x8000000000000000</Keywords> 
  <TimeCreated SystemTime="2013-05-08T13:44:26.464456100Z" /> 
  <EventRecordID>295475</EventRecordID> 
  <Correlation /> 
  <Execution ProcessID="532" ThreadID="4960" /> 
  <Channel>System</Channel> 
  <Computer>myserver.ms.tasb.org</Computer> 
  <Security UserID="S-1-5-18" /> 
  </System>
 <EventData>
  <Data Name="AlertDesc">10</Data> 
  <Data Name="ErrorState">1203</Data> 
  </EventData>
  </Event>