Hello Nick,
Looks very strange to me. The error log doesn’t tell very much. Only that there was a writing error on file C:Config.Msi11a50b.rbf. Was 12-Dec-11 1:01:47 AM the date and time when you installed ECSync?
Perhaps you could give write access to the administrator the the mentioned file or folder. I’m just guessing.
In fact I don’t know why Windows tries to reconfigure ECSync. Especially not when an Office application is launched. Never had this before. Does reinstalling Office help?
Sorry
Thomas