Blackberry Enterprise Server 5 troubleshooting

We are having a BES 5 with an Exchange 2010 SP1 /hosting switch environment. 3 Organizations in Exchange. 2 Organizations work fine with their Blackberry's. 1 Organization is having troubles. GAL lookup is failing and emails from same Organization are having a wrong 'from' email address format: instead SMTP the Exchange format EX. Therefore User cannot reply to this email using his BB-> "no valid email address found". We suspect it to be an Active Directory permission problem. We did investigate but did not find the source of the problem. We are looking for an experienced troubleshooter who can help us solve this problem. Ideally we would stay in contact for future projects.