I had a separate issue from the original poster. Just a flat-out crash after a few minutes of using the program. After trying a bunch of random things, I finally got a useful error message, citing a GPF in an unrelated file. Turned out to be a SVGA driver, which (it turned out) had a known bug that could cause system crashes in Win98. Sadly, after upgrading the driver, I still had crashes-and recently, I got another error message citing the same driver. (Usually the whole system just freezes, and I need to either Ctrl-Alt-Del twice or, sometimes, hard reboot.)
Data source has never been the problem, although I updated those DAO and Jet drivers before I'd isolated the SVGA driver as a trouble source.