Hej Jesper,
afaik we haven't done changes in this area so will need to investigate.
Could you open a bug on https://jira.jboss.org/jira/browse/JBIDE with details and preferably also with a screenshot of the server editor ?
One basic thing to check is if the username/password is set correctly in the UI ?
i.e. check that this user/password combo is correct?
btw. could you - just for "fun" :) try and swap the values of username/password ?
i.e. if its admin/secret then type in secret/admin
There was a bug where the two fields were swapped but I don't think that was in M5 (but worth a shot to checkout)