Getting the similar error here, this is a fresh install of Rev. 2 I used the IONetworking.kext provided above and that got rid of the MAC Address cannot be found error.

3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Backup requested due to disk attach
3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Starting standard backup
3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Error: Volume at path /Volumes/Backups does not appear to be the correct backup volume for this computer.
3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Backup failed with error: 18

WOOT! I don't know what the problem was... I went to Time Machine Pref's turned Time Machine to Off, clicked change Backup Disk; selected the same disk and it works!

3/19/08 12:37:11 PM /System/Library/CoreServices/backupd[272] Backup requested by user
3/19/08 12:37:11 PM /System/Library/CoreServices/backupd[272] Starting standard backup
3/19/08 12:37:11 PM /System/Library/CoreServices/backupd[272] Backing up to: /Volumes/Backups/Backups.backupdb
3/19/08 12:37:11 PM /System/Library/CoreServices/backupd[272] Event store UUIDs don't match for volume: Hackintosh
3/19/08 12:37:15 PM /System/Library/CoreServices/backupd[272] Backup content size: 452.3 GB excluded items size: 436.1 GB for volume Hackintosh
3/19/08 12:37:15 PM /System/Library/CoreServices/backupd[272] No pre-backup thinning needed: 19.52 GB requested (including padding), 75.70 GB available

Well Snowman, looks like you've got a little update to occupy yourself with for a while:
http://osx.kbot.de/comments.php?DiscussionID=799

**Bump**

Would like to know if anyone got TM working, I have somehow.. just curious.

Yes I've it working and have re-installed a full back up from it.

Ive had it working fine, you just need to press yesterday in a folder window the first time to kick it past the crash it gives the first time you try to look at your backups.

And network timemachine kext fix prob helps a little too.

Good Luck

I don't have a clue what happend here. No matter what I don't even get the slightest progress with this issue.

I think I tried just about anything now. And I won't give into trying the new Zeph release. I've done my share of reinstalls for now.
Hopefully it'll start working without any reason some day, cause that's how it got broken too inthe first place.

You guys using GUID or MBR drive partition?

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 Snow Leopard 10.6.7  Gigabyte GA-P35-DS3P  Intel Q6600 @ 3Ghz  Corsair CM2X2048-6400DHX  Gigabyte HD5770 Silent Cell  Samsung SyncMaster 2494SW  ALC889a  Creative T5400 5.1  Maxtor 380215AS  Pioneer DVR-215D  Presonus Inspire 1394  KRK Rokit 5  Wacom Bamboo One 
 SL USB Guide => http://www.infinitemac.com/f57/guide...k-drive-t3705/ 

both fail in my experience.

22/03/08 22 maart 16:34:22 System Preferences[258] Failed to get MAC address for machine
22/03/08 22 maart 16:36:47 [0x0-0xc00c].com.apple.finder[166] Unexpected reply from backup server - ignored
22/03/08 22 maart 16:36:47 [0x0-0x29029].com.apple.systempreferences[270] Unexpected reply from backup server - ignored
22/03/08 22 maart 16:42:27 System Preferences[295] Failed to get MAC address for machine

Is the MAC address error important for this issue?

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 Snow Leopard 10.6.7  Gigabyte GA-P35-DS3P  Intel Q6600 @ 3Ghz  Corsair CM2X2048-6400DHX  Gigabyte HD5770 Silent Cell  Samsung SyncMaster 2494SW  ALC889a  Creative T5400 5.1  Maxtor 380215AS  Pioneer DVR-215D  Presonus Inspire 1394  KRK Rokit 5  Wacom Bamboo One 
 SL USB Guide => http://www.infinitemac.com/f57/guide...k-drive-t3705/ 

yes, time machine uses a disk-specific ID that is somehow based on or compared to the MAC adress of your computer. google once told me this, but I cannot find the page right now.

when you check your startup log, you'll probably see that there is an error message that "no network card can be found" or alike. I guess this is the same issue.