In org.modeshape.jcr.JcrRepository on line 944 the correct root cause of a JAAS login exception is swallowed, this makes it hard to find the problem:

// Need to make sure that the user has access to this session
try

{ session.checkPermission(workspaceName, null, JcrSession.JCR_READ_PERMISSION); }

catch (AccessControlException ace)

{ throw new NoSuchWorkspaceException(JcrI18n.workspaceNameIsInvalid.text(sourceName, workspaceName)); }