I upgraded my operational blog from an old version of CVS to the current version. All my stub file blogs broke (including the a_stub sample stub). The problem was the inability to find the NT_ function. I was able to fix this by requiring my _config.php file in each of my stub files. Not sure if this is the real fix but it did get me up and running again.
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CVS isn't really stable right now. We have just reorganized so many things that these kind of glitches are no surprise. We should fix this shortly...