Yes, it should work with LDAP authentication. Perhaps there is some slight difference in the usernames between LDAP and the file that was used to upload those students? Have you checked the user table in the Moodle database? Also I understand you made some changes in the Moodle code in your installation (c.f. http://moodle.org/mod/forum/discuss.php?d=6829#32271) Perhaps that could be the problem?
General help
Enroling Students
This discussion has been locked so you can no longer reply to it.