Strange FireWire Issue

I purchased a WD External 80gb Hard Drive (combo USB/FireWire). My PC is as
follows:
ASUS A7N8X with built in FireWire and USB
WinXP Pro
AMD 2600 Processor
512 ram

The external drive works great via USB, but when I use it with FireWire, I
get all kinds of data corruption and errors. Ex. picture files become very
distorted, MP3 files will not hardly play.
Western Digital replaced the drive and the new drive does the exact same
thing. Could the built in FireWire be the problem? I thought of buying a PCI
FireWire card but did not want to waste $ if it was actually the drive.

Thanks

--
Kevin

Hal Parr