Confirmed. Looks like in dmNavigation/webtopBody.cfm it loads the value of the default site tree location as an ObjectID. (Actually, on my system its 2 UUID separated by a comma for some reason) but the code expects an alias value (‘home’, ‘root’, etc) so this fails. So, two problems, why is the user edit form setting the “overviewHome” property to 2 comma separated UUIDs and why does the webskin seem to expect an alias instead of a UUID. IMO, it should work with both.
You will need to edit the user and re-save to fix the data problem as the duplicate IDs will have been saved to the database, then the user will need to log out and log back in.