ldap syntax help requested

[shouldbworking]

I'm getting the annoyingly non specific One or more errors occured during the processing of a command message whilst trying to get a list of users in an OU.

LDAP://172.16.xxx.x/OU=anou,DC=domain,DC=asubdomain;(&(objectCategory=person)(objectClass=user));

Can anyone see whats wrong with this? thanks