If you downloaded the latest alpha build zip, you should have working tree examples in the examples folder. These have been updated to reflect the current naming conventions. You'll run into problems trying to match the blog version with the right code, because it's about a month old and based on a pre-alpha build.
The working TreePanel component was in the 0.40 version which I still have and use. I took it from SVN before that 1.0 version came in. Do you want a copy of it?
SVN is currently unavailable as there as some changes being made in its administration and access. In any case, the latest alpha code is what's in the build zip (SVN was not current). I imagine this will continue thru the beta cycle, until things stabilize and access to SVN is re-addressed based on support level.