freebsd stable - Aug 2007 - Leading blank in username

I run FreeBSD 6.2 and 6.1 in my mail servers. I use ldap via pam for 
authentication. The output of the commands:
id "username"
id " username"
is the same (user and group number) if username is defined in ldap 
database, while the second one issues "user unknown" if username is 
defined in passwd file.
Someone has found this problem?

                                Thanks, Fulvia