MSI error - Sophos Anti-Virus -- Configuration failed.

I am having trouble with a machine, it won't update. I have protected again but makes no difference. For some reason it won't let me manually uninstall SAV as it says I am not a Sophos admin, which is not true.

The log file says at the end (Sophos Anti-Virus Major Install Log_121001_100059)

MSI (s) (D4:28) [23:02:50:522]: Note: 1: 1729 MSI (s) (D4:28) [23:02:50:522]: Product: Sophos Anti-Virus -- Configuration failed.

MSI (s) (D4:28) [23:02:50:537]: Cleaning up uninstalled install packages, if any exist MSI (s) (D4:28) [23:02:50:537]: MainEngineThread is returning 1603 MSI (s) (D4:E4) [23:02:50:646]: Destroying RemoteAPI object. MSI (s) (D4:3C) [23:02:50:646]: Custom Action Manager thread ending. === Logging stopped: 01/10/2012  23:02:50 === MSI (c) (D0:1C) [23:02:50:646]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be

denied.  Counter after decrement: -1 MSI (c) (D0:1C) [23:02:50:646]: MainEngineThread is returning 1603 === Verbose logging stopped: 01/10/2012  23:02:50 ===

2012-10-01 23:02:50 ERROR: Installation failed

I can't post the whole thing as it is large, and contains sensitive info.

Can anyone help with this please?

Thanks