Requesters from certain Accounts cannot log in

Hi,
I am experiencing a peculiar problem with requesters and the possibility to log in.

I have 2 different accounts (Account A and Account B).
When a user from A tries to log in to SDP, SDP shows the error message "Wrong username or password" (I have checked, doubble checked and trippled checked the password, I am entering the correct).
When a user from B tries to log in to SDP it works perfectly.

Account A was set up prior to B.
I have tried to create a new requester on A, but it still shows to same error message, even though the new requesters WAS NOT imported through CSV.

Worth noting is: During the set up of Account A, SDP crashed several times, and I cannot with complete certainty say it affected the account in some way.

Is it possible for me to check how the account "is feeling" in the database?