The latest beta has a bug.
It uses FILE_DIRECTORY_TEMP, which doesn't exist. Drupal 6 provides a function file_directory_temp() for this, though.
I think it only surfaces in PHP 5.3 but not sure. Anyway, it's a bug and it should be fixed.
I couldn't get HEAD to work, so this is against the latest beta.

Patch attached.

CommentFileSizeAuthor
drutex-undefined-constant.patch909 byteststoeckler