My guess is they updated the XML.
From:
Code:
<OnUpdate>CastingBarFrame_OnUpdate(self,elapsed)</OnUpdate>
To:
Code:
<OnUpdate function="CastingBarFrame_OnUpdate"/>
The first creates an intermediate function that calls
CastingBarFrame_OnUpdate(), the second sets
CastingBarFrame_OnUpdate() as the handler. This is why the hook worked pre-7.0.