I've been banging my head against the wall over this issue for the last couple weeks.
This issue is affecting at least 10 of our endpoints.
I have tried numerous things, including -
Stopping AutoUpdate service, clearing AutoUpdate's cache folder, restarting AutoUpdate service.
Manually uninstalling all Sophos components - AutoUpdate and AntiVirus refuse to install due to invalid package.
Grabbed the .MSI of the same version from another endpoint, and tried uninstalling using that .MSI on the affected endpoint - Sophos still claimed it was invalid.
I have run a Diagnostic log, the archive can be found here - https://drive.google.com/folderview?id=0B5lFgMDR2tQjRXFhZkpRUkhWNms&usp=sharing
If you need to see specific logs, please let me know.
This thread was automatically locked due to age.