Just a thought, is content module (cck) coming through after your change and resetting it? Give your module a lower weight in the system table to test if something else is overriding your change.

>I have a hook_nodeapi op='view' implementation that is changing $node->content['body']['#weight']. Apparently it is being ignored because every other section that has a weight higher (less negative) than that weight is still being rendered above the body. I haven't yet gone digging through core to find out why this is happening. Is this the correct behavior?