We have CQ 5.3 set up using LDAP authentication. We have one user who has been using CQ with her AD Userid/password for over a year with no issues, but she came in one day and now it's saying her user id and password don't match.
We've tried on multiple different instances of CQ and she gets the same message every time. She is able to log into other applicaitons that use LDAP for authentication just fine. We have tried resting CQ to see if that resolves the issue and it hasn't. I originally thought it was some sort of issue with her LDAP account, but because she can log into other apps, I'm wondering if not? Or maybe there WAS an issue with her account, but it was resolved (she thought maybe her account was locked, so she ran an unlock procedure), but CQ just hasn't caught up to that fact? This started happening a week ago.
Have you tried running a manual LDAP User sync for the single user (http://localhost:4502/crx/config/ldap.jsp)? Since the user can login to other systems via LDAP, the problem is most likely with their account in CQ. Maybe try deleting their account in CQ and re-creating/re-sync via LDAP User sync.
Hope this helps.