Newly-detected BPMs are forgotten if too many are scanned

Using Mixxx 1.9 on Ubuntu 10.10, Intel Core2 Duo (2.13 GHz)

I've moved a lot of tracks into a new crate, many of them from different folders, genres, etc.
Many of these have not been scanned, so I've been loading them into decks individually (not ideal, I know, but the BPM Analysis can't scan by crate). After loading each track, the BPM is (usually) detected, and I go on to the next track.

However, after loading about 10-15 tracks, I'll keep going, and all the previously-detected BPMs are no longer there, they're all back to 0.
If I keep trying to find BPMs, by loading another track in, it will give that track's BPM, but upon loading another, it will immediately forget the previous track's BPM.

In the console, whilst finding new BPMs, I get:
Debug: [Main]: Track Played: "Happy Mondays" - "24 Hour Party People"
Debug: [Main]: TrackDAO::getTrackLocation QThread(0x1a19e10, name = "Main") "qt_sql_default_connection"

Whereas, after the BPMs stop being detected, for whatever reason, there is no TrackDAO line, just a "Track Played".

So far, it seems the only way to get this crate's BPMs detected is to load about 10 tracks, close Mixxx, then re-open and repeat, which, naturally, is somewhat annoying.