create postgresql datasource with datasource manager

Hi every body

I have a problem to create a postgresql datasource in BI server.
Here are the steps I followed :
1 - Install ubuntu server (12.04 LTS)
2 - Install postgresql 9.1
3 - Install open-jdk7
4 - Install Pentaho BI Server
5 - Install postgresql jdbc connector (postgresql-9.3-1100.jdbc41.jar in /tomcat/lib)

Using another computer, I try to connect in pentaho ! ==> everything is ok
but when I want to create a datasource using datasource manager i have an error :


also, the database is remotely accessible.

Where is the problem ? can someone help me please ?

Thanks in advance