As noted early Apple has just released the new Mac OS X 10.5.7. You can update your Mac via Software Update in the Preferences. When Apple introduce 10.5.6 update. DFU mode was broken and this conflicted with a lot of people who needed to jailbreak their iPhone and iPod Touch. The only solution was to use in some cases a USB Hub or use the 10.5.5 IOUSBFamily kernel extension.
With the new Mac OS 10.5.7 DFU mode session are fully functional, which is certainly a good thing! We can also synchronize notes between the iPhone 3.0 and iTunes 8.2 via USB. Take a Look at a screenshot by Mark Sfreddo that shows the ability to synchronize notes in iTunes.
More info could be found here:
http://support.apple.com/kb/HT3397