System hangs during on-access scanning of encrypted disk images

I have experienced the exact same problem.

Computer: Macbook Pro, Core i7, Mac OS 10.7.2, internal flash drive encrypted with FileVault 2. Fresh Sophos install.

Time Machine backup drive: external 1 TB drive attached via USB 2.0. One encrypted partition.

To set up an external drive as an encrypted volume in Mac OS X 10.7, go to Time Machine in System Preferences, unlock it, click "Select disk", select the external drive, and check "Encrypt backup disk" before clicking "Use Backup Disk". Time Machine will repartition the drive, destroying anything on it, and make it one big encrypted partition. You will need to provide a password and hint for the disk (not your login password) and you can store this pasword in your keychain. Time Machine can encrypt the drive in the background while your backup is underway; this background encryption can take hours.

After this point, Sophos will randomly hang the machine. This manifests as processes blocking indefinitely as soon as they try to access any disk (internal, external, whatever). This includes the background encryption process.

The workaround that I have found that works is to tell Sophos not to scan the backup drive by putting its path (/Volumes/something) into the ignore list. This has worked fine so far, with no lockups.

(I fail to see the utility of Sophos creating panic over files that were purged years ago yet still present on the backup. I just had to deal with Sophos digging up an email attachment from 2006 that had a Windows virus, then claiming that it could not be cleaned up and directing me to a page with a Windows-based cleanup tool, which is silly because I can't run the cleanup tool.)

I have experienced the exact same problem.

Computer: Macbook Pro, Core i7, Mac OS 10.7.2, internal flash drive encrypted with FileVault 2. Fresh Sophos install.

Time Machine backup drive: external 1 TB drive attached via USB 2.0. One encrypted partition.

To set up an external drive as an encrypted volume in Mac OS X 10.7, go to Time Machine in System Preferences, unlock it, click "Select disk", select the external drive, and check "Encrypt backup disk" before clicking "Use Backup Disk". Time Machine will repartition the drive, destroying anything on it, and make it one big encrypted partition. You will need to provide a password and hint for the disk (not your login password) and you can store this pasword in your keychain. Time Machine can encrypt the drive in the background while your backup is underway; this background encryption can take hours.

After this point, Sophos will randomly hang the machine. This manifests as processes blocking indefinitely as soon as they try to access any disk (internal, external, whatever). This includes the background encryption process.

The workaround that I have found that works is to tell Sophos not to scan the backup drive by putting its path (/Volumes/something) into the ignore list. This has worked fine so far, with no lockups.

(I fail to see the utility of Sophos creating panic over files that were purged years ago yet still present on the backup. I just had to deal with Sophos digging up an email attachment from 2006 that had a Windows virus, then claiming that it could not be cleaned up and directing me to a page with a Windows-based cleanup tool, which is silly because I can't run the cleanup tool.)