After upgrading to version 5.0, when deleting a user the OnBeforeDelete handler in the CustomDataHandler class with the following method signature is no longer called:

OnBeforeDelete(string className, int id, object conn)

The OnBeforeDelete handler with the following method signature is called, but former method is not called:

OnBeforeDelete(object dataObj, object conn)

I have not tested this with deleting other types to see if they are affected as well.