High Point Ultra ATA Controller Chip

I recently have been installing Abit's BE6 Mb in several new systems I have built. Windows Installation goes fine and the system seems stable passing burnin and other benchmark tests. Send the unit home and the unit comes back with corrupt hard drives. Files and Directory's missing. Maxtor and WD drives in all units and all using the BE6 MB with the Ulta ATA 66 controller. Current Bios, current controller drivers, Win98 SE. Problem is hard to nail down and the tech from ABit has been no help. Problems always seem to happen when the system is rebooted. It has to be a timing issue but I can't nail it down. Would appreciate any input.

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I wish I knew what I was doing.