CiviCRM Event participants being removed without notice

Drupal 6 + CiviCRM 3.4.8 on a linux box.
We are having problems with participants being dropped from the event without any action on our part.
Their contact records stay intact, but are altered to remove them from their event.
No evidence of these removals in the database or the logs.

It does not happen on a daily or hourly basis, but maybe something closer to a weekly basis. We believe the last time this happened was between the hours of Saturday 8AM to Sunday 8AM. Cron runs hourly, but we believe it is still something related to a cron action as all administrators have been blocked until this is resolved.

I took notice that it might be related to people registering multiple participants, as a noticed removal of participants were people that were registered using the multiple participants function.