DCOM errors on new Small Business Server + Domain

Hello.  We recently set up a lot of new equipment for a client of ours.  They previously had no domain, no Windows servers even.  Now they have a SBS 2011 (Exchange not configured, mostly just being a DC, DHCP server, file and print server).  They also have a 2008 R2 remote desktop services server living with the SBS on a VMWare ESXi host.  

Their workstations aren't new, but mostly everything else is.  We've been adding workstations (mostly Windows 7) to the domain, and everything has been going fine.  Now that we've mostly wound down from that, looking at the server I see the following error several times:

Log Name:      System
Source:        Microsoft-Windows-DistributedCOM
Date:          4/8/2011 10:33:25 AM
Event ID:      10009
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      server.network.local
Description:
DCOM was unable to communicate with the computer pc.network.local using any of the configured protocols.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-DistributedCOM" Guid="{1B562E86-B7AA-4131-BADC-B6F3A001407E}" EventSourceName="DCOM" />
    <EventID Qualifiers="49152">10009</EventID>
    <Version>0</Version>
    <Level>2</Level>
    <Task>0</Task>
    <Opcode>0</Opcode>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2011-04-08T14:33:25.000000000Z" />
    <EventRecordID>22189</EventRecordID>
    <Correlation />
    <Execution ProcessID="0" ThreadID="0" />
    <Channel>System</Channel>
    <Computer>pc.network.local</Computer>
    <Security />
  </System>
  <EventData>
    <Data Name="param1">pc.network.local</Data>
  </EventData>
</Event>

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They get this for several PCs on the network, it doesn't seem to be all of them, but most.  They don't seem to be having any issues, that I can see.  They can access network resources fine, they can print fine, they can log in fine.  This error seems to appear several times every half hour, though it doesn't seem to affect the end users at all.  

I have googled around and found some information that didn't seem to help, one involved modifying some GPS objects that get applied to the workstations to allow unsolicited traffic from the server's IP address.