Hi Andrew,
This looks very similar to an issue that I had ~5 months ago, but on version 5.0. In my case, sfcbd watchdog was exhausting inodes causing the host to become unresponsive (as per the links posted by MKguy).
I had a support case logged with VMware who provide a hot patch to address this, but this has long been superseded. In between VMware providing the hot patch, I needed to monitor all hosts to make sure I that I could restart the hosts well in advance of any unplanned downtime and saved my bacon on two separate occasions with a PowerShell monitoring script.
Here are some links to my original posts;
http://communities.vmware.com/thread/430571?start=0&tstart=0
http://communities.vmware.com/thread/431987?start=0&tstart=0
I've updated the script quite significantly since my posts and continue to monitor in the background as a matter of course, but as random as the issue appeared it seemingly disappeared.
Might be worth logging this one to VMware?
Cheers,
Jon