Are you using any third party (non-core) modules like Dynamic Registration? Is there an event logged in your log viewer when the user is deleted? if not can you check to see if that option is turned on?

To turn on user deletion logging follow these steps:
1. Log-in as an admin or host
2. Go to the Log Viewer
3. Hover over the module actions drop down in the top left of the container (looks like a little triangle) and select "Edit Log Settings" from the list.
4. Scroll through the list and look for "USER_DELETED".
5. Click the pencil icon next to it.
6. Make sure that Logging is Enabled, and that it is set for all portals and is set to keep at least 10 log entries.
7. Click "Update" if you made any changes.

If you do get a log entry for this user delete event, could you post that here?

Thanks,

-Nathan

Well, if you see a log entry, then that means that the user is being deleted via the DNN application and not directly in the database. Moreover, if you are not using any third party user management modules, that really narrows down the possibilities. Are you sure that the user is not doing it, perhaps unintentionally? If you go to your profile, then click on Manage User Credentials, there is a "UnRegister" button that any user can use to delete there account. perhaps the user is clicking that, thinking that it will unregistered them from a mailing list, or email notifications, etc. If your sure that the user is not doing it, then post back here and I'll see if I can come up with any other ideas. Another thing to check is you could try and turn on logging for user logons and see if a particular user logs in to the system just prior to that user being deleted.

-Nathan