I've recently updated from TortoiseSVN 1.7.6 to 1.8.2 (linked against SVN 1.8.1). For one of the subfolders of my working copies I ran into this error: E170000 'x' isn't in the same repository as 'y' where x used to be an svn:external, which has been deleted before updating the SVN client, even so the subfolder containing the external was deleted before, so this is error virtually hunting a ghost! This is a true blocker, I cannot update anymore! There is no way for downgrading working copies from 1.8 to 1.7, also creating a new checkout is not an alternative, since a) the server connection is slow as it is located on another continent and b) this has to be done for multiple working copies in a continuous integration system.
Original issue reported by ingmarvoigt