Hi,
The database was recorded with binary descriptors in the BOW dictionary. In 0.10, the kd-tree cannot be used as nearest neighbor approach for binary descriptors, change it to BruteForce approach. See Preferences (advanced) -> Visual Word, scroll down for "Nearest neighbor strategy". You may also want to use the same feature type as in the database, at the top of the same panel (which would not be SURF or SIFT).
Note that with 0.11 (latest version), kd-tree can be used with binary descriptors.
Overall, you should always use the same feature type as in the database. Unfortunately, we may forget which feature was used in a old database. I opened an
issue for an option to load parameters from a database.
cheers