Actually... I think I fixed it.
I removed the .rockbox directory, got the latest build, put it on, then initialized the database (which worked on a fully-charged iPod).
I suspect it might've been one or more of the following three things:
* The DriveBox theme I was using
* The fact that I had done so many hard reboots trying to get things to work (thus corrupting something)
* Some setting I'd made when trying to get things to work, inadvertently affecting RB's performance (I was having other problems too, like RockBox freezing when pausing a song played in File mode, crunching through the hard drive for long periods of time, taking forever to play a select a new song, etc.)
So, anyway, it seems things are working fine now.
UPDATE: I'm almost positive it was the DriveBox theme. I don't know if it's too memory-intensive for my iPod or what... it's a shame, as it's a very nice, readable theme.