There is no file named pro.pl in the CalendarScript distribution AFAIK.
I suggest you change the permissions of that file so it is not executable and/or delete the file (after making a copy) and contact Matt directly via email and report as much details (access log records of access to that file, etc.) as you can.
JMO
Dan O.
[This message has been edited by DanO (edited May 21, 2004).]