Did you find out anything? I have this same issue, no warning, debug shows nothing but that it received a message to disconnect. Happens quite often. Not working for offsite backups at all. Did you get any help?I do not have any NAT going on, just the tunnel.
Hi Tom sorry for the late reply. I'm afraid I can't give you anymore info as it started working perfectly without NAT and with this hotfix from the other discussion: http://support.microsoft.com/kb/2523881/en-us