If you disable on-access scanning in Sophos for Microsoft SharePoint, items continue to be blocked.
This occurs if your on-access anti-virus policies were set to 'Block Access'.
Sophos for Microsoft SharePoint
What to do
This is known SharePoint behaviour.
SharePoint exhibits the same behaviour when simply disabling the 'Scan documents on download' option in its 'Antivirus Settings' page - it will not allow an already-blocked item to be unblocked.
Microsoft will be fixing this issue in the next SharePoint service pack. Until then there is a Microsoft hotfix package to fix this issue.
See http://blogs.msdn.com/sowmyancs/archive/2008/07/11/how-to-enable-users-to-download-infected-files-when-a-download-scan-that-is-performed-by-using-anti-virus-software-is-disabled.aspx .