cannot update sophos and cannot unlock preferences

Dear all,

I'll try to be very brief... I am running OSX 10.7 and the autoupdate of Sophos seems deactivated (see attachments). In the beginning everything was working fine with version 8...  a couple of months ago, I realised that the autoupdate and manual update stopped working and were grey (attachement).. could not find a solution, so I decided to uninstall version 8 and try to install version 9, which I did ... for a couple of hours (probably until next reboot) everything worked fine, after that the problem came back... and not only, now on version 9, i cannot even unlock the preferences...

I know it is highly unlikely, i even performed a complete scan (which is apparently running and working) without any negative result, but it i have the same feeling as when a process or undesired "object" is blocking autupdate and preferences access to avoid being removed or so... in a few words, the tipical virus/malware behaviour...the mac is maybe a bit slower but I did not recognize any strange things though.....

any ideas on how to solve this?

Thanks

Luca