This bug does not actually affect Authentication in my set up, it affects Enrolment. But I believe the issue is occuring at Authentication, so I'm posting it here.

AD Authentication is fully functional with the distinguishedName mapped to idnumber set to update on every log on. However, AD Enrolment fails. I believe it fails because of some things happening with the setting and updating of idnumber. The CN of our users are stored as "lastname, firstname". Because of the comma, AD stores the CN as "lastname\, firstname".

The first time a user logs on to Moodle, the idnumber is mapped and stored correctly as:
CN=Student\, Test,OU=eLearning,OU=Students,DC=ccsmj,DC=com

On second and subsequent log ons the idnumber is modified and stored as
CN=Student, Test,OU=eLearning,OU=Students,DC=ccsmj,DC=com

In both cases enrolment fails.

However, if I set the mapping of idnumber to only occur on creation, and manually store the idnumber as
CN=Student
, Test,OU=eLearning,OU=Students,DC=ccsmj,DC=com

Both Authenticatioin and Enrolment function properly.

I decided to try the double backslash format after reading the issue at http://moodle.org/mod/forum/discuss.php?d=35865#226068 which dealt specifically with broken Authentication.