Because most third-party disk utilities cannot repair the current boot volume, utility developers usually provide their products on a bootable CD. You then boot your Mac from the CD to repair or otherwise work with your normal startup volume. One issue that has always plagued utility developers is that when new Macs are released, these new Macs often require a newer version of the Mac OS than otherwise available, so the current utility CDs cannot be used with these models.
As a result, disk utility developers periodically release new CDs, with updated/newer versions of the Mac OS that can (hopefully) be used as bootable CDs on all current Mac models.
The recent conflicts between Panther and FireWire drives has raised an interesting, and unfortunate, issue: what if the newer version of the OS provided on those CDs is itself problematic? MacFixIt reader Greg Earle reports on the recently released TechTool Pro 4.0.1:
"The CD it comes on is a Mac OS X bootable CD - this is good news. The *BAD* news is that the CD comes with Mac OS X 10.3 on it, *not* 10.3.1!!!"
(Greg is referring to the fact that the initial version of Panther -- OS X 10.3 -- had a known conflict with many FireWire drives, reported extensively here on MacFixIt, where restarting with those drives connected could result in the drive's directory being irreversibly damaged. The problem was officially acknowledged by Apple as affecting FireWire 800 drives with specific firmware versions, but many MacFixIt readers reported similar issues with other drives, as well. Apple announced that a "fix" for the problem was included in Mac OS X 10.3.1, and updating to Mac OS X 10.3.1 indeed fixed the problem for many users.)
Booting your Mac from a TechTool Pro 4 CD that contains OS X 10.3, instead of the "fixed" 10.3.1, may be dangerous for users with FireWire drives connected that are susceptible to 10.3's FireWire bug. We have contacted Micromat about this issue and will post any information they provide us about the potential for data loss when using this CD and/or any solutions or workarounds they will be providing. Until then, we recommend disconnecting FireWire devices while booting from such CDs.
However, this issue may also affect other disk utility vendors who have recently updated their CDs to include OS X 10.3, and began producing those CDs before OS X 10.3.1 was available.