Hi One of our clients are saying that one of their sites in their server farm is losing permissions? She says that the one day she just started getting access requests for the users on the specific site? they have quite a few sites and it only happens on this site?!?! Is this a bug that anyone know of?? Can this happen?? Or was it someone who fiddled with the permissions....??

Not a sharepoint bug, and no it doesn't happen. Most probably a User Error :-)