I have the same problem with my IA1. The problem has also been noted for the latest versions of the i-opener manufactured in summer/fall 2000 (version 5's--earlier versions enable DMA just fine). I have spent much time on the DMA issue for the i-opener and conclude it is a bios/hardware issue that might be resolved by some registry poking in software once someone sorts things out. For the i-opener this is a possibility, since the bios is completely hacked. For the IA1, I think it is unlikely that anyone will bother.
I recommend you follow the work of "Georgie" on this board in the i-opener section to see what's going on with DMA and also with USB corruption issues and poor PCI bus speeds. The last two are other "fixable in software" bios problems that may be applicable to the IA1 since the chipset is the same as in the i-opener--VIA MPV4.
Keep in mind that these devices were never intended for serious IDE hard drive work, and the bios's have never been tweaked for such work. Even without DMA enabled, you can get IDE throughputs of up to 16MB/sec if your 4200 rpm hard drive is up to it and your pci bus is tweaked. This should be plenty fast enough.
jimmy aka "klunk"