Fairly minor - but a user pointed this one out to me.
If you go to create (submit) an event within the
calendar - but click on the previous or next month
within the calendar block using either "<<" or ">>"
then you get an error - "sorry you cannot access this
file directly."
Presumably the block is inheriting the module.php as
the current page and trying to pass the ?date variable
to it as it would to the index.php.