i've attached a few files in the hopes that you can solve this.
Screenshot #1.jpg and
Screenshot #2.jpg are the dialogs that describe the alarm that was set up i believe in february of 2011.
assuming that i am looking at the right file that contains all of the tasks, events, etc. (Default.ics in a .rainlendar folder) the following two files contain snippets of that file
ICS (Before).txt is a snippet after the alarm should have popped (on 10/5) but before i "Completed" it.
ICS (After).txt is a snippet after i "Completed" it.
as far as your statement of
what needs to be done that the alarm doesn't trigger anymore i'm not sure what you are looking for. i set the alarm up in february 2011 and at some point the recurring alarms stopped popping up which was indicative of one of the bugs fixed in the 112 beta. so there is really nothing that needs to be done from my point of view. the alarms simply do not pop up when they should.
i'm reluctant to move my clock ahead for testing for fear of messing any time dependent stuff i have installed on my system.
if i get a chance i may try to test this in a virtual environment however i'm suspecting that new tasks that are created will work correctly since the "recurring alarm bug" was fixed in beta 112. however, the question i pose is, does this fix correct the issue for already existing tasks that were set up prior to beta 112. this is one of the reasons why i attached the "Before" and "After" ICS files.