Outlook won't reconnect to Exchange Server

After the backend email server was rebooted to remove a virus, Outlook did not reconnect for some users.  Both servers have now been rebooted, services have been restarted. Mail is flowing between the back-end and front end servers. Still some users show disconnected and there is no checkbox next to Work Offline. Rebooting their PC's does not help.   Problem seems to be spreading slowing. I have checked the connections per another case here. Very few connections there. Any ideas?

Log Name:      Application
Source:        Microsoft-Windows-Search
Date:          5/15/2009 1:23:27 PM
Event ID:      3036
Task Category: Gatherer
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      twood-l1.ouraddomain.com
Description:
The content source <mapi://{S-1-5-21-1975004227-1061043541-810500426-2381}/> cannot be accessed.
 
Context:  Application, SystemIndex Catalog
 
Details:
	(HRESULT : 0x80004005) (0x80004005)
 
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-Search" Guid="{CA4E628D-8567-4896-AB6B-835B221F373F}" EventSourceName="Windows Search Service" />
    <EventID Qualifiers="32768">3036</EventID>
    <Version>0</Version>
    <Level>3</Level>
    <Task>3</Task>
    <Opcode>0</Opcode>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2009-05-15T20:23:27.000000000Z" />
    <EventRecordID>1136</EventRecordID>
    <Correlation />
    <Execution ProcessID="0" ThreadID="0" />
    <Channel>Application</Channel>
    <Computer>twood-l1.ouraddomain.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data Name="ExtraInfo">
 
Context:  Application, SystemIndex Catalog
 
Details:
	(HRESULT : 0x80004005) (0x80004005)
</Data>
    <Data Name="URL">mapi://{S-1-5-21-1975004227-1061043541-810500426-2381}/</Data>
  </EventData>
</Event>

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