Prior to this change, Prototype treated only the event names present
in the Event.DOMEvents array as native DOM events. Now, Prototype
looks for the presence of the namespace delimiter -- a single colon --
to determine whether you're observing a custom event or a native event.
You'll need to update any code that uses 1.6.0_rc0's "contentloaded"
event to use its new name, "dom:loaded." You'll also need to give
namespaces to any other custom events you may be firing or observing.
We suggest using singular nouns for namespaces, and past-tense verbs
for the event names (e.g. "effect:queued", "widget:activated", and so
on).
-sam