We encountered this problem with different versions of OS & Subversion on the server side, the following details being the same:
- We used https protocol to access the SVN repositories.
- We used Apache HTTPD + mod_dav_svn + mod_authz_svn. We also used either mod_auth_kerb or mod_auth_gssapi.
- The users authenticated with Windows Integrated Authentication. Members of a certain group were allowed to access the SVN repos.
- The clients were Windows workstations, with fairly recent SVN versions (1.13-1.14).
Some clients worked OK, others got a HTTP 400 Bad Request error on accessing the SVN repository. On the server side the error manifested in a "NO AUTH DATA Client did not send any authentication headers" message in the SSL error log.
Some users consistently succeeded, others consistently failed to access the SVN repos.