[Owncloud] oc 4.03.: problem in installation

[Freeze NorthPole]

Hi guys,
yesterday morning i' ve installed (correctly) owncloudn 4.03 in server with
debian 6.0.3, it was very awesome but
after some tentative   i've decided to reinstall it, recreating the
directory and recreating the database,
but at the end of the installation the application trying to reach the url:

http://mydomain.com/owncloud/index.php

i recieve the folllowing message:

MDB2 Error: connect failed: _doConnect: [Error message: unable to
establish a connection] [Native code: 0]

could you help me to resolve this problem??

thanks a lot