[Serusers] 500 Internal server error

MessageI am trying to call people that are registered in SER, but then I get a "500 Internal server error". The logs don't show anything I can understand and the people are registered correctly. What is going on? If I send a call that begins with 0 the call is successfully relayed to a gateway. I have this problem only with registered users. Example: User Siderite logs in. User Sid2 logs in. Siderite calls a) Sid2 b) Sid2(a)domain.com The result is identical: 500 Internal server error. Could it eb linked with the problem with the acc module, as I haven't been able to succesfully log any accounting yet. I am using SER 0.9.0, but I had the same issues with 0.8.14.