There have been some reports of FireWire 400 drives losing Data as well. This update does fix SOME issues related to the problem (I am guessing iPod related issues), but they still say to upgrade your drives FirmWare in case.
It also has some updates to help with FileGuard as well as a few security Updates
Apparently some sites have retracted reports of issues with FW400 drives. I have a Lacie FW400 drive, so I'd be interested if anyone has any links to confirmed reports and/or firmware updates for FW400.
Only firewire drives or enclosures with the Oxford Semiconductor 922 (OW922) OHCI Bridge controller are affected. Since only USB 2.0/FW800 or FW800-only enclosures use this chipset (FW400 drives use the OW911 bridge), then in all likelyhood, FW400 drives such as the iPod will not be affected.