Problems installing Sophos AV on x86_64 Linux

Hi,

I'm trying to install Sophos AV version 7.1.3 onto a x86_64 Scientific Linux 5.5 system (equivalent to RHEL 5.5).

The installation very nearly completes, but I get the following:-

Installing Sophos Anti-Virus....
Selecting appropriate kernel support...
When Sophos Anti-Virus starts, it updates itself to try to find a Sophos kernel interface module update. This might cause a significant delay.
Sophos Anti-Virus starts after installation.

Installation completed.
Starting Sophos Anti-Virus daemon:                         [  OK  ]

NOTE: You are running Sophos Anti-Virus on a kernel for which Sophos provides the Sophos kernel interface module only as source. Therefore this module has
been locally compiled. In most cases this module will work. However, Sophos reserves the right not to provide support where any such compilation has taken
place.
Sophos will use reasonable endeavours to provide first line support. Should issues arise that require second line support, or any other escalation process,
Sophos cannot guarantee that such issues will be resolved.

Starting Sophos Anti-Virus GUI daemon:                     [  OK  ]
Sophos Anti-Virus GUI is available for configuration at http://localhost:8081/

Installation aborted.
Bad magic number in /opt/sophos-av/bin/_/savdstatus

 The contents of /opt/sophos-av/install.log:-

Traceback (most recent call last):
  File "SavForLinux.py", line 21, in main
  File "Controller.py", line 105, in action
  File "Controller.py", line 429, in __install
  File "Controller.py", line 561, in __checkSavd
  File "ActionSupport.py", line 171, in runSavdstatus
ImportError: Bad magic number in /opt/sophos-av/bin/_/savdstatus

In addition, the first time I run savupdate it fails (output anonymised):-

Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/server.inf
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/savlinux/server.inf
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/savlinux/cidsync.upd
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/cidsync.upd
74357 bytes downloaded in 0.022122 secs (3.205492 MiB/s)
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/manifest.dat
110056 bytes downloaded in 0.034274 secs (3.062300 MiB/s)
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/config/index.spec
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/talpa-custom/index.spec
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/cac.pem
1131 bytes downloaded in 0.008939 secs (123.558424 KiB/s)
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/mrinit.custom
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/MRInit.custom
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/mrinit.conf
543 bytes downloaded in 0.007797 secs (68.009907 KiB/s)
Downloading http://antivirus.somewhere.ac.uk/Sophos_update/savlinux/master.upd
318 bytes downloaded in 0.006912 secs (44.928702 KiB/s)
Automatic update aborted
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "Updater.py", line 631, in main
  File "Updater.py", line 599, in tryRun
  File "Updater.py", line 561, in run
  File "Updater.py", line 322, in doUpdateAndRecordResult
  File "Updater.py", line 120, in tryUpdate
  File "Updater.py", line 95, in update
  File "CidUpdater.py", line 242, in update
  File "CidUpdater.py", line 182, in updateFromTopLevelCidsync
  File "CidUpdater.py", line 77, in updateFromCidsync
  File "CidMulti.py", line 203, in skeletonUpdate
UnboundLocalError: local variable 'updated' referenced before assignment

The second and subsequent times I run it, it works fine.

Apart from these errors everything else seems to be working fine but is there something wrong?