Installation Error

I'm getting the following error when I try to install Sophos for Mac.

20/09/2011 19:39:04.554 com.apple.SecurityServer: Failed to authorize right 'system.install.app-store-software' by client '/System/Library/PrivateFrameworks/PackageKit.framework/Versions/A/Resources/installd' [3857] for authorization created by '/System/Library/CoreServices/Installer.app' [3816]

20/09/2011 19:39:04.587 installd: PackageKit: ----- Begin install -----

20/09/2011 19:39:20.942 installd: PackageKit: Install Failed: Error Domain=PKInstallErrorDomain Code=112 "An error occurred while running scripts from the package “SophosUI7.2.7.pkg”." UserInfo=0x7fdf5aa44440 {NSFilePath=./postflight, NSURL=file://localhost/Volumes/Sophos%20Anti-Virus%20Home%20Edition%20OS%20X%2010.4%2B/Sophos%20Anti-Virus%20Home%20Edition.mpkg/Contents/Packages/SophosUI7.2.7.pkg, PKInstallPackageIdentifier=com.sophos.ui.7.2.7.installer, NSLocalizedDescription=An error occurred while running scripts from the package “SophosUI7.2.7.pkg”.} {

    NSFilePath = "./postflight";

    NSLocalizedDescription = "An error occurred while running scripts from the package \U201cSophosUI7.2.7.pkg\U201d.";

    NSURL = "file://localhost/Volumes/Sophos%20Anti-Virus%20Home%20Edition%20OS%20X%2010.4%2B/Sophos%20Anti-Virus%20Home%20Edition.mpkg/Contents/Packages/SophosUI7.2.7.pkg";

    PKInstallPackageIdentifier = "com.sophos.ui.7.2.7.installer";

}

20/09/2011 19:39:21.609 Installer: Install failed: The Installer encountered an error that caused the installation to fail. Contact the software manufacturer for assistance.

I've removed the two Sophos directories from Applications, the directory from Library, and the 3 plist files from LaunchDeamons and retried, but it fails to install every time. I'm using a MacBookPro running Lion.

I think it did install correctly first time, however my machine ground to a halt so I ran the uninstaller and removed it. I'd like to try again, however it's now not installing. After these failed installs, the uninstaller does not think it's installed (fair enough I guess) and I delete manually.

Any thoughts, tips?

CB