Filevault decrypt failure

Question

My usual backup method requires turning off Filevault. However, when trying to do so I get the error: *"an error occurred: an error occurred during decryption (an error occurred during copying). Filevault will be turned on for this home folder and the home folder will still be encrypted"*. I ran disk utility verify disk and repair disk permissions to no avail. I still get the error.
I am running 10.4.10, 2gRAM, 2.33 IC2D MBP.
Help?

Answer 1

Perhaps one of the following will help:
http://docs.info.apple.com/article.html?artnum=303617
http://docs.info.apple.com/article.html?artnum=303617
http://www.macosxhints.com/article.php?story=20050326041757989
Solving File Vault Related Problems
Syd Low offered a helpful tip about recoving damaged Mac OS X FileVault data:
Apple's knowledge base article on this problem - How to verify or repair a home directory image - didn't work for me. When you click repair at step 12 Disk Utilty will not be able to repair the volume because of permission problems. Here's what I did:
I added write permission using the command line. Open the Terminal (Utilities folder) and at the prompt enter the following commands pressing return at the end of each:
prompt > cd /Users/accountname
prompt > sudo chmod g+w accountname.sparseimage
You will be asked to enter your admin password. It will not be echoed.
prompt > sudo chmod g+w /Users/accountname
Now you can run Disk Utility to repair the image successfully. Remember to change the permissions back afterwards:
prompt > sudo chmod g-w accountname.sparseimage
prompt > sudo chmod g-w /Users/accountname
Also read the following in the event the above doesn't help:
FileVault-protected Home shows less capacity than what's available on the hard disk.
Some possible fixes if FileVault goes awry.