Suddenly can't back-up with Time Machine

Question

Time Machine has finally completely quit. I have followed most of the suggestions on various Apple forums, including reformatting the backup HD (several times), repairing both the back-up and main HD, settting spotlight to private, quitting Finder (using Tinker tool), etc. Followed Pondini's very useful steps repeatedly. I get different error messages from Time Machine Buddy most every time. The most consistent refers to indexing.
Below are the three most recent Buddy logs, in hopes somebody can help. Or suggest another backup solution.
Starting standard backup
Backing up to: /Volumes/Hitachi Orange/Backups.backupdb
Ownership is disabled on the backup destination volume.  Enabling.
Detected system migration from: /Volumes/Macintosh HD 1
Backup content size: 498.4 GB excluded items size: 460.7 GB for volume Macintosh HD
No pre-backup thinning needed: 45.22 GB requested (including padding), 930.58 GB available
Waiting for index to be ready (101)
Indexing a file failed. Returned 200 for: /System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/wx-2 .8-mac-unicode/wx/lib/inspection.pyc, /Volumes/Hitachi Orange/Backups.backupdb/Galloway Desktop (3)/2011-07-08-190340.inProgress/F18A8582-E9F7-4D93-9BA0-07DEB1749449/Macintosh HD/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/wx -2.8-mac-unicode/wx/lib/inspection.pyc
Aborting backup because indexing of file failed.
Stopping backup.
Copied 60774 files (16.3 GB) from volume Macintosh HD.
Copy stage failed with error:11
Backup failed with error: 11
The one before
Starting standard backup
Backing up to: /Volumes/Hitachi Orange/Backups.backupdb
Detected system migration from: /Volumes/Macintosh HD 1
No pre-backup thinning needed: 37.67 GB requested (including padding), 877.17 GB available
Indexer unavailable (200)
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x102e0a4b0 "The file “classes.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x102e0cf10 "The file “info.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x102e0cf10 "The file “keyedobjects.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x1005312b0 "The file “classes.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Copied 0 files (35 KB) from volume Macintosh HD.
Backup canceled.
And before that
Starting standard backup
Backing up to: /Volumes/Hitachi Orange/Backups.backupdb
Detected system migration from: /Volumes/Macintosh HD 1
No pre-backup thinning needed: 37.67 GB requested (including padding), 877.17 GB available
Indexer unavailable (200)
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x102e0a4b0 "The file “classes.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x102e0cf10 "The file “info.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x102e0cf10 "The file “keyedobjects.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Error (256): fetching properties: Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x1005312b0 "The file “classes.nib” couldn’t be opened." Underlying Error=(Error Domain=NSPOSIXErrorDomain Code=5 UserInfo=0x103004520 "The operation couldn’t be completed. Input/output error")
Copied 0 files (35 KB) from volume Macintosh HD.
Backup canceled.
Any help would be most appriciated.
This is my iMac (Late 2010) running OS X 10.6.8, backing up to a 1Tb Hitachi external HD, connected directly (no hub) via usb.

Answer 1

It's possible that the system was keeping some piece of the I/O error in memory and, after the underlying cause of the I/O error went away, something you did juggled the system's brain back to a non-error condition.
You are absolutely correct to remain suspicious of your HD. While it's possible that changing USB cables or zeroing out the disk might have solved the underlying I/O problem it's equally possible that you have a failing drive on your hands that may only be showing ugly symptoms sporadically. There is a small risk that you will end up with two sets of damaged data if a drive fails during data transfer so it was very wise of you to order another drive.
You might want to consider using Carbon Copy Cloner or Super Duper! to make a clone to your new drive. Having a TM backup and one or more clones, all on separate physical drives, is a very effective backup solution. That's the combo I use.
When my Mini's internal drive failed it took about five minutes to boot from one of my clones, restore a few files from my TM backup, set TM to back up the clone, set SuperDuper to back up to my second clone. After that, I was fully back in business by booting from my clone which allowed me to get the Mini's HD repaired when it was convenient for me.