Outlook anywhere Sync issues

We have a client running SBS 2011 and all of the clients have full access and sync capabilities with the exchange server with one exception. One client has a Vista home premium machine that he retrieves email from. We installed Outlook 2010 and set up outlook anywhere. Cached mode is on, logon network secuity is set to negotiaite authentication, connect to exchange using http is checked, and all proxy settings are valid. The customer will sporadically have gaps in delivery and sometimes gets messaging errors on sent items. Approximately twice a day (no specific time) he gets the following error message:

8:46:41 Synchronizer Version 14.0.6109
8:46:41 Synchronizing Mailbox 'xxxx xxxxxx'
8:46:41 Terminated in error
8:46:41              [8004010F-501-0-1710]
8:46:41              The client operation failed.
8:46:41              Microsoft Exchange Information Store

So far none of the standard troubleshooting steps have worked.
I have:
Disabled and re-enabled cached mode
Removed and reinstalled his profile
Recreated his OST file.
Reinstalled outlook 2010

For the most part his mail service reception and delivery is immediate, but it will get hung up in the pattern stated above. There are no entries in his his event viewer under system or application logs that correspond to these sync issues