I am having the same issue. I am on 10.7.5. It has been a few days with the menu shield being gray. I opened up preferences and on-access scanning is disabled but there is no way to get it turned on again, because it is greyed out. I removed shophos and reinstalled with same result. Please help.
Do no appear to have an issue with the server. Can update catalogue. But still getting "Fatal Error:Unable to initialise virus detection engine" in log.
On access scanner off message and occasional pop-ups telling me Sophos is not running. Seeing issues on both Mac Mini & Macbook Pro. Were running OK several weeks ago.
As the kba states, the issue is that the 8.0.8 update did not fully install -- this means that the virus detection engine won't run.
Is your version currently at 8.0.8.1?
If it's at 8.0.8, you can either run the update from the menu item to upgrade and fix the issue (if it's the one people have been experiencing with the 8.0.6 -> 8.0.8 upgrade), or uninstall Sophos, remove the Sophos plist preferences files, restart your computer and re-install Sophos. The upgrade is likely the easier path.
