Javascript errors prevent page moves

In some of our spaces at wikis.sun.com, we noticed that when we try to move a page a javascript error is thrown when the page tree loads.

It looks like this error prevents the page to be highlighted in the tree and that makes it impossible to move the page to a new location.

Error: node is null
Source File: https://wikis.sun.com/s/1325/4/1.0/_/download/resources/confluence.web.resources:page-ordering-tree/tree.js
Line: 80

and

Error: node is null
Source File: https://wikis.sun.com/s/1325/4/1.0/_/download/resources/confluence.web.resources:page-ordering-tree/tree.js
Line: 89

I'm not sure if depth is a factor, but all of the pages that I see right now are 5 or more levels deep in the tree hierarchy.