I have same problem. However observed that students get de-listed after a few days of enrolement into the course. I have had to manually enrol them again a couple of times. Any idea why this is happing and how it can be resolved?
We are currently using Moodle ver 1.5.3
with php5 version 220.127.116.11 and mysql version 4.0.24
OS is Edubuntu kernel-release 2.6.12-10-386 on an i686 Machine.