Re-install of Client Access Role failing with 0x800700B7 error

Having some serious problems getting activesync working on an exchange 2007/server 2008 standard 64 system.

I was receiving a 0x085010004 error when trying to sync a windows mobile 6.0 device with the server, on playing around with the virtual directories, I kept receiving a "cannont locate mbx" error when trying to edit permissions on the "Exchange " virtual directory.

I decided to re-install IIS7 and the remove & reinstall the client access role.

when trying to re-install the client access role, I get the following error:

========================================
Summary: 2 item(s). 1 succeeded, 1 failed.
Elapsed time: 00:14:58


Copy Exchange Files
Completed

Elapsed Time: 00:11:47


Client Access Role
Failed

Error:
An error occurred while creating the IIS virtual directory 'IIS://dmserver1.dmservices.local/W3SVC/1/ROOT/Autodiscover' on 'DMSERVER1'.

Cannot create a file when that file already exists. (Exception from HRESULT: 0x800700B7)

Elapsed Time: 00:03:11
========================================
 The only virtual directories created from the failed install is "owa" & "Exchweb"

Any ideas will be appreciated.

TIA.

Mark