SOME WINDOWS 7 AND VISTA COMPUTERS UNABLE TO DOWNLOAD UPDATES FROM WSUS

We have some Windows 7 Pro (x86 and x64) and Vista (x86) computers that use to download and install updates from our internal WSUS just fine, but something has changed in the past 2 months.  These computers are now unable to download any updates from our internal WSUS and reports that they need no updates from the local Windows Update Agent interface. However if these computers are pointed to Microsoft’s Windows Update (instead of WSUS) then they are able to download install updates without any issues.  Below is the WSUS log from two such computer affected by this problem.

2013-11-22    12:25:21:413    3892    df4    PT    +++++++++++  PT: Synchronizing server updates  +++++++++++
2013-11-22    12:25:21:413    3892    df4    PT      + ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = https://wsus.domain.local/ClientWebService/client.asmx
2013-11-22    12:25:33:383    3892    df4    PT    +++++++++++  PT: Synchronizing extended update info  +++++++++++
2013-11-22    12:25:33:383    3892    df4    PT      + ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = https://wsus.domain.local/ClientWebService/client.asmx
2013-11-22    12:25:33:400    3892    df4    DtaStor    WARNING: Attempted to add URLhttp://wsus.domain.local/Content/A2/8BB20B389AC34A742EDE4F91608DF4CB3728F2A2.cab for file i7ILOJrDSnQu3k+RYI30yzco8qI= when file has not been previously added to the datastore
2013-11-22    12:25:33:400    3892    df4    DtaStor    WARNING: Attempted to add URLhttp://wsus.domain.local/Content/4A/03875066450C0CA429EC4E0DB469D46403085A4A.cab for file A4dQZkUMDKQp7E4NtGnUZAMIWko= when file has not been previously added to the datastore
2013-11-22    12:25:33:400    3892    df4    DtaStor    WARNING: Attempted to add URLhttp://wsus.domain.local/Content/5B/844D8D69B0ED22CE2DFDF1353B01A32D3D6F1F5B.cab for file hE2NabDtIs4t/fE1OwGjLT1vH1s= when file has not been previously added to the datastore

All of these affect computers have these similar warnings, but these Update IDs don’t exist on our WSUS server.
 
WARNING: Attempted to add URLhttp://wsus.domain.local/Content/5B/844D8D69B0ED22CE2DFDF1353B01A32D3D6F1F5B.cab for file hE2NabDtIs4t/fE1OwGjLT1vH1s= when file has not been previously added to the datastore

2013-12-03    10:11:34:018    3720    146c    PT    +++++++++++  PT: Synchronizing server updates  +++++++++++
2013-12-03    10:11:34:018    3720    146c    PT      + ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = https://wsus.doamin.local/ClientWebService/client.asmx
2013-12-03    10:11:39:661    3720    146c    PT    +++++++++++  PT: Synchronizing extended update info  +++++++++++
2013-12-03    10:11:39:661    3720    146c    PT      + ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = https://wsus.doamin.local/ClientWebService/client.asmx
2013-12-03    10:11:39:677    3720    146c    DtaStor    WARNING: Attempted to add URLhttp://wsus.doamin.local/Content/AB/127C5B4E0A5B70160A6DB67D1F79B641A7CAF7AB.cab for file EnxbTgpbcBYKbbZ9H3m2QafK96s= when file has not been previously added to the datastore
2013-12-03    10:11:40:160    3720    146c    Agent    Update {1A7FDF41-48D6-4C90-B7E8-026F7F4133DC}.1 has no local extended metadata. Not returning it.
 
 
Same error as the other computers, but with a different *.cab file.
 
    2013-12-03    10:11:39:677    3720    146c    DtaStor    WARNING: Attempted to add URLhttp://wsus.doamin.local/Content/AB/127C5B4E0A5B70160A6DB67D1F79B641A7CAF7AB.cab for file EnxbTgpbcBYKbbZ9H3m2QafK96s= when file has not been previously added to the datastore
 

Our WSUS server is running Windows Server 2008 R2 Standard with WSUS 3.0 SP2 (3.2.7600.256) and all Microsoft updates including KB2734608.

Any suggestions on fixing this growing problem?