Applescript stopped working under Snow Leopard - Error -1700

I use Event2ToDo (an AppleScript function) to create ToDos in iCal on a daily basis. It is a very helpful tool, and I really want to keep using it. That being said, under Snow Leopard it doesn’t work anymore. Specifically, the line that gets the error is…

tell application “iCal” to set convertMePosList to uid of (every event in thisCal whose open file alarms is not {} and start date is less than or equal to (current date))

And it says…

error “iCal got an error: Can’t make {} into type open file alarm.” number -1700 from {} to open file alarm

I think, from what I could discern, it’s trying to say “whose open file alarms is not blank.” Does anyone know how to fix this to work under Snow Leopard?