So I was getting this problem using our LDAP server with Juniper SA4000 where it would accept your password (it wouldn't give you an error), but it would redirect you to the login screen. In the policy tracing, it would say "Login failed. Reason: OK". grrrrr

So going to "User Realms"/Realm Name/"Authentication Policy" and disabling 'Enable Password Management' seems to be a decent workaround.