I don't have a lot about this right now, I am researching this issue still, but I wanted to drop a brief line about something I have just started to see. The kinds of encryption failures I recently, and in the past have reported, maybe restricted to data being reported in only a 'corrupted users' account.
Within the last few days I have examined a file sent to me that shows 'encryption errors' in some Customer Credit Card numbers; however, these encryption errors only show up under one specific QuickBooks users' account. When that user logs into their Company file, and clicks on some specific customers they receive the QuickBooks warning about the customers' credit card data having encryption/decryption (corruption) issues. In some cases the customer credit card number field may contain 'no information' and in other cases it may contain 'odd characters' (as this particular user calls them.)
When other users on the same system, accessing the same data file, check the same specific customer record they DO NOT receive the QuickBooks warning. Further when they examine the customer's credit card number field it appears normal.
At first I believed this odd behavior might be the result of a 'bad installation of QuickBooks' on the specific users computer; and so I did a complete (clean) uninstall/reinstall, but got the same results under the user's log-in. I further confirmed that it was not a 'installation issue' on the specific machine by logging in under several different user credentials, and each of those users did not experience the encryption/decryption issues with any customers. This almost 100% confirmed that the problem was associated with the original users QuickBooks user account.
In order to test this, I created a new User account for the individual, insuring identical permissions as the previous account. The result: when the individual logged-in using their new User account, on their regular computer, they DID NOT experience the encryption/decryption corruptions. (Note: I did NOT delete the old user account, and do not recommend that anyone ever do so.)
The Verify Utility neither showed encryption/decryption issues with any customer, nor did it show that the User's account was corrupted. But the differential diagnosis procedures I performed in deed confirm that the reported encryption/decryption errors the user was experiencing under their original User account must be the result of corruption of that User account and not the 'database' as a whole.