Bitcoin passphrase fail steps to reproduce: I installed bitcoin-qt version 0.8.1 around March 22, 2013. I let it sync for about 48 hours until it was completely up to date. No error messages. I set my wallet passphrase with an 11 char mixed case alphanumeric. CapsLock was off. I wrote down my passphrase on paper and stored it in two separate fire resistant vaults. I created a receive address and received coin sent from mtGox. I let the transaction verify by more than six hosts. I created a new address for offline storage and sent the coin to it. I waited for at least six verifications. I created two backups of the wallet. The two backups compare exactly via windows comp command. I stored the backups on USB drives in two separate fire resistant metal vaults. I exited bitcoin. It was not set to start automatically on system login. I did not execute bitcoin for the next eight months. No block updates. Windows Auto Update was on.

On November 19, 2013 I started Bitcoin again for the first time in eight months. As Bitcoin attempted to sync it produced many identical error messages something like: “failure to read block”. After each error I stopped and restarted the program. The errors occured at random intervals on average about an hour apart. Trying to eliminate the error messages I upgraded to version 0.8.5 while version 0.8.1 was running, and I saw no error messages. I restarted the computer. Bitcoin continued to fully sync receiving blocks with no more error messages. Next, for the first time I checked the box “Start Bitcoin on system login”. I observed over the next 10 days that bitcoin 0.8.5 remained sync'd with no error messages.

On November 28, 2013 I attempted to change my passphrase and received the error: “The passphrase entered for the wallet decryption was incorrect.” CapsLock was off. Same keyboard, same system (except for Windows Update).

I backed up my wallet and compared the new backup to the two previous backups. The Windows “comp” command reports the new backup is different from the two previous backups as

follows:

dir 04/09/2013 12:40 PM 73,728 Long Term Savings Bitcoin Wallet.dat 11/28/2013 04:48 PM 73,728 New Backup after passphrase fail msg.dat 04/09/2013 12:40 PM 73,728 Wallet Backup 2013 04 09.dat

comp Name of first file to compare: Long Term Savings Bitcoin Wallet.dat Name of second file to compare: Wallet Backup 2013 04 09.dat Option: Comparing Long Term Savings Bitcoin Wallet.dat and Wallet Backup 2013 04 09.dat. .. Files compare OK

Compare more files (Y/N) ? y

Name of first file to compare: New Backup after passphrase fail msg.dat Name of second file to compare: Long Term Savings Bitcoin Wallet.dat Option: Comparing New Backup after passphrase fail msg.dat and Long Term Savings
Bitcoin Wallet.dat... Compare error at OFFSET 8014 file1 = 6 file2 = 4 Compare error at OFFSET 8016 file1 = 34 file2 = 0 Compare error at OFFSET 8017 file1 = 16 file2 = 1C Compare error at OFFSET 801A file1 = D4 file2 = 78 Compare error at OFFSET 801B file1 = 1B file2 = 1F Compare error at OFFSET 801C file1 = 34 file2 = 0 Compare error at OFFSET 801D file1 = 16 file2 = 1C Compare error at OFFSET 801E file1 = 78 file2 = D4 Compare error at OFFSET 8020 file1 = FC file2 = A0 Compare error at OFFSET 8021 file1 = 1B file2 = 1F 10 mismatches - ending compare

Question 1.) Does bitcoin-qt version 0.8.5 intentionally produce a different .dat backup than 0.8.1?

So, I shutdown bitcoin-qt and replaced wallet.dat with the March 22, 2013 backup. (in C:\Users\MyUserName\AppData\Roaming\Bitcoin) and restarted fully sync'd with no error messages.

Once again, I attempted to change my passphrase and received the error: “The passphrase entered for the wallet decryption was incorrect.” CapsLock was off. Same keyboard, same system (except for Windows Update).

Question 2.) Any suggestions?