I have installed my Symfony project on another computer with the same specifications, and I receive the following error when I login with fosuserbundle:
You might have set a wrong password in your parameters.yml because of which it might not be able to connect to the DB.
The above mentioned error occurs when the app is not able to connect to DB to check if the user is authentic.
(I also faced the same error and this was my problem, hope it helps)