Sophos Auto-Updates are causing Laptop to Freeze

I have been having a problem for a couple of months, which is now getting worse, related to Sophos auto-updating.

Sometimes when it is updating the computer will freeze for 5min to several hours (it is currently doing the latter):
- usually the first sign is that firefox or thunderbird will say not responding and grey out slightly
- then in some sequence other programs will say not responding (in the beginning part of this problem I can use other programs like Excel)
- Task Manager will not open
- sometimes after long pauses there will be responses to previous clicks (an excel file will be saved for example)
- during this, the mouse *is* responsive and I can typically toggle between open windows using Alt-Tab
- the clock sometimes stops updating part way through
- every time this happens Sophos is in the process of updating
- eventually the freeze stops and (most of the time) the computer functions normally.

I have run literally a dozen virus checks and that is not an issue.

There is a consistent set of lines in Windows Event Viewer which occur just as the updating troubles begin:

Error 6/14/2012 12:43:25 PM SAVOnAccess 81 None " The on-access scan of file ""\Device\HarddiskVolume1\ProgramData\Sophos Web Intelligence\s ..."" of process mbamservice.ex, start check timestamp [ 1cd4a53cd486cc1] did not complete in time: file was not scanned.
"
OR
Error 6/13/2012 1:24:59 PM SAVOnAccess 81 None " The on-access scan of file ""\Device\HarddiskVolume1\ProgramData\Sophos Web Intelligence\s ..."" of process mbamservice.ex, start check timestamp [ 1cd499071ed829f] did not complete in time: file was not scanned.

This suggests a conflict between Sophos and Malwarebytes Anti-Malware. However the problem persists even when:

- I have turned off MAM (turned off real time protection)

- excluded Malwarebytes folders (c:\programdata\malwarebytes AND c:\ proram files (x86)\malwarebytes' anti-malware) from sophos' scanning

I also have other lines related to Firefix and Thunderbird in the Event Viewer. I have added exclusions to these folders as well in Sophos.

At this point I have given up and turned off auto-updating all together.

If anyone has any suggestions on what might be going I would greatly appreciate it!

My machine:
Dell Latitude E6320
Win 7 Enterprise x64
Sophos Endpoint Security and Control version 9.5
Windows Firewall On
No other Antivirus/Firewall programs installed (I previously had malwarebytes installed but have disabled it and the problem persists: see above)

PS I did see a related thread, /search?q= 1043 , but am not sure how this was resolved.