I wish I could help more... well here's another guess: - if you are using XML / XMLList, and have used insertBefore / isertAfter from the same XML / XMLList, then it is a known bug. - if you dispatch "collectionChange" on your own you might have messed something in the event's properties, which then will make the collection run in a loop thinking it's being updated over and over again. It is slow, but it isn't that slow to run out of script timeout limit :) Anyways, bindings are the first suspect in such case, but if that's not... ah, and, why won't you debug it? the debugger should be able to look into the framework sources. If, for whatever reason it doesn't, copy the Tree and other classes involved into your project and try debugging this way.
Best. Oleg