Spent all day writing a debug engine into the RomanLaw project in order to figure out what was causing some very odd behaviour, in which queries worked on one table but failed on another identical table. There are three options:

1. PEAR's MDB2 library is broken. There are some indications of previous bugs in this area, and the documentation for MDB2 is poor. We can only test this by rewriting the whole site to use DB, or pure mysql functions. This is probably what I'll have to do tomorrow.
2. mySQL is flaky on the dev server. Some odd behaviour when we tried to drop tables suggested this might be the case, but we have dropped and rebuilt the entire database several times.
3. There's a mismatch between our PHP version and our mySQL version (in other words, PHP is expecting a more recent mySQL, or doesn't work well with precisely the version we have). This is less likely (although it is the case on Mustard).

I'm going with option 1 tomorrow; Greg is looking into the mySQL logs to see if there's any sign of 2 or 3.