[Building Sakai] help with SAK-17261 "disappear student problem with Sakai and LDAP integration"

[Zhen Qian]

Hi, all:

SAK-17261 (Students disappear from class roster) has been reported as a
problem since 2.6.  It was marked as Blocker and was down-graded to
"critical" recently.

A bit of description here: 
"We are using Course Management module to automatically enroll students
into the appropriate courses. Our home-grown software populates cm_* tables
in Sakai database with appropriate records. This system worked fine until
upgrade to version 2.6.0. For *some* courses *some* students repeatedly
disappear from class roster. The students re-appear after "Site info" page
is visited, but disappear again in a few minutes after that. All data
entered into the gradebook for these students disappear quickly."

This might be a problem with JLDAPDirectoryProvider only. Since I don't
have a working instance of LDAP server, it is hard for me to debug this. 
So it would be greatly appreciated if some other Sakai universities using
LDAP servers would help with the problem.

Thanks!

- Zhen