AppleScript-based rule only works manually

Question

Greetings,
I have set up numerous Rules to automatically move messages to specific folders, based on Subject headers. These work automatically, as new mail comes in.
However, one of my Rules is set up to "Run Applescript." The script deals with a single file that gets e-mailed to me by one of my webservers at 11:00 each night. It deletes the previous night's file from the HD, grabs the new attachment, saves it to the HD, and deletes the message in Mail. The script works correctly, but the Rule (which is set as Active) only works when I select the message and do it manually (Command-Option-L) -- not automatically when the message arrives.
Why is this?
The script, which lives in /Library/Scripts/Mail Scripts/Rule Actions, is below.
Thanks!
DM
<hr>
using terms from application "Mail"
    on perform mail action with messages theMessages for rule theRule
        tell application "Mail"
            repeat with thisMessage in theMessages
                set theAttachment to first item of thisMessage's mail attachments
                set theAttachmentFile to theAttachment's name
                tell application "Finder"
                    if exists "iBook:Users:me:Documents:" & theAttachmentFile then
                        delete "iBook:Users:me:Documents:" & theAttachmentFile
                    end if
                end tell
                save theAttachment in "iBook:Users:me:Documents:" & theAttachmentFile
                delete thisMessage
            end repeat
        end tell
    end perform mail action with messages
end using terms from

Answer 1

I would start by verifying that the rule is in fact firing - add a set color of background action before the run applescript action.
Next I would try a few magic incantations:
change the script location to ~/Library/Scripts/Applications/Mail/
remove the "for rule theRule" from the on perform
add an on run handler after the end of the existing script
using terms from application "Mail"
on run
tell application "Mail" to set sel to selection
tell me to perform mail action with messages (sel)
end run
end using terms from
Why? 'cos any scripts that I have successfully run from a rule are like that! The 3rd one has the advantage that you can apply your script to selected messages, which can be useful (though not in the present case).
If none of this works, it is time to try some serious debugging. You could consider putting in an try ... on error with a display dialog for the error message, or simply a display dialog on script entry to verify that it is running.
Let me know ...
AK