I tried the things suggested in the previous posts.
I also sent up some crash dump files last week however I have not heard anything back yet.
Also did some more testing and found that as soon as a GPO which enabled 'Offline files and folders' was applied it BSOD. It did this a couple more times and then stabilized. We have now had a machine running for a few days now running the full install of SEP11 MR5 i.e. with network threat protection and it seems to be OK.
So if you are having any issues have a look to see if you are enabling 'offline files' via a GPO as this could be the cause.
Please post any thoughts.