I found we where running on a modified eztreemenuoperator.php to get this menu to function.
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Høgskolen i Lillehammer
Lillehammer University College http://www.hil.no
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Messenlien IT http://messenlien.com
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Instead of modifing the treemenu, you should make a copy of the operator, and make a new one (called treemenu2 or something) and put it in an extension. That makes it much easier to catch these troubles in the future, and also much easier to upgrade.
Also its a good idea to do the upgradecheck for database and files in the administrator interface (setup->upgrade check)