On a plain Debian server with two virtual servers set up (a main site at example.com and a dev site set up as a subserver at dev.example.com), errors started appearing when attempting to commit files via svn. Here's an example of one of the errors:
Commit failed (details follow):
Sensitive names have been replaced with "private".
After fiddling with permissions for a while and coming up empty, I ended up exporting the repo, deleting it from the server (which I had to do manually since the "Delete" button didn't do anything and no error was shown) and re-importing it. I was then able to commit files as expected.
This isn't the first time this has happened. In all cases, developers are trying to commit over https (e.g. https://firstname.lastname@example.org/svn/private) and the intervention listed above has been the only way I know to fix it (other than deleting the entire virtual server and re-creating it, which isn't an option most of the time).