"Mike, I had a problem with my FW800 port not working with my new AL 24" 2.8 GHz right after delivery in August. Two new FW 800 drives (AC powered) wouldn't mount. I was convinced that the iMac was defective and called AppleCare to get a replacement. I was not particularly patient while the Apple rep had me go through a few routine procedures. He had me zap the PRAM. That didn't work. (Of course smarty pants me, I just "knew" it wouldn't.) Then he had me:

1. Shut down the computer.
2. Disconnect all devices and all other cables, except the keyboard and mouse cable(s).
3. Disconnect the computer from the power outlet and wait for 3 to 5 minutes. (this also resets the SMU/PMU on G5 towers)
4. Plug the computer back in and turn it on.
5. Reconnect the device(s) (one at a time if there is more than one) and test. Test with each port if you have more than one.

Of course I just "knew" this wouldn't work either but I went through the steps so I could get a replacement iMac. OMG - It worked! And my FW800 port has continued to work ever since! Later I found this apple doc on What to do if your computer won't recognize a FireWire or USB device which outlines this procedure.
I hope it can be of some help to others.
-Dana"

Disconnecting/reconnecting has been an old tip for issues with USB devices (like printers, UPS, etc.) after OS X updates also.
If the above (or earlier tip below - using a recognized FW device in the chain between the iMac and the problem device) helps with a FW problem you've had, let me know the details. Thanks.

v3.0.1 (11), October 23, 2007
• Fixed an issue that caused creating new disk images to fail
• Fixed an issue that would cause backup to a remote Macintosh to fail
• Fixed an issue that caused "Failed to chown" messages to appear in the log and caused CCC to report that the synchronization engine had failed
• Modification times of folders and applications are now properly preserved when using the "Copy everything" cloning method
• Fixed an issue in which locked files were not properly deleted (as necessary)
• Fixed an issue in which CCC reported that it could not enable ownership on the target volume
• CCC now explicitly disallows non-HFS volumes (this clears up confusion on what target volumes are supported)
• Fixed an issue in which CCC errantly reported that it could not archive some items during a "Copy selected items" clone
• Resolved several localization issues and included localizations for French, Russian, Korean, Swedish, and Dutch
• The Authentication Credentials Installer package no longer installs CCC's version of rsync into a location commonly in $PATH
• Minor tweak to improve performance when copying to a sparse disk image created by CCC on a network volume
• Fixed an issue that would cause some target volumes to not be bootable
• Fixed a cosmetic issue in which the amount of data copied in the CCC.log file was grossly incorrect

You can download it at the Carbon Copy Cloner home page. (v3 is for OS X tiger and later, CCC version 2.3 download is also there for users of OS X 10.2 and 10.3.)

"...For bus-powered FW devices and other lower power devices, try using a powered device between the iMac and the scanner. We have had some success with this method. Give it a shot.
(name withheld by request)"

BTW - the iMac owner that mentioned problems with some FW scanners later replied his solution was similar - the 2 FW scanners not recognized when directly connected were recognized if they were connected (daisy-chained) to a FW device that was recognized (in his case a 3rd scanner that was recognized with a direct connect).

For those with bus powered FW device problems (although there could still be a bridge board/firmware/driver issue or just another case where some have problems and not others even with the same hardware) - the Apple developer Docs note 7W of power per Firewire port - so check the wattage listed for your bus powered device. Many portable drives have a jack for an AC adapter which is worth trying if you have one. (I'd also try the drive with another mac and if possible run a disk repair utility on it.) A powered FW hub may or may not help (just make sure the FW hub is designed for the bus voltage - in the past some FW or FW/USB powered hubs went up in smoke when connected to macs with 24V or higher FW bus power (like the G5 tower and some earlier towers) but not sure what the intel-based Mac's FW voltage is.)
Yesterday's post also had some links to tips on other Firewire issues (FW audio issues, Migration assistant tips, etc.)
Update - see later post above for other tips for FW (or USB) devices not recognized.

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• RapidWeaver 3.6.4 now Leopard Ready
• More to Mac Sales than a halo effect
• Moving beyond the iPod
• A review of 'Fake Steve's' new real book. It's vintage faux Jobs
• iPhone is the 4th best selling phone in the US
• Comcast to face lawsuits over BitTorrent filtering
• FCC Cracks Down on Analog TV Retailers
• 2007 International Design Excellence Awards (IDEA)
• Cisco buying WiMax start-up for $330 million
  
  Apple Support/Troubleshooting Doc Updates:
• Aperture: Working with images shot in black and white
• iPhone: Default Email Client error message during Sync
• .Mac, iWeb: About page hit counters on your mac.com pages
• Logic Studio: How to install content to a different location
• iTunes Wi-Fi Music Store Troubleshooting
• iPod displays "Use iTunes to restore" message
• About iTunes Store authorization and deauthorization