I recently began getting CC-800 error on my Community America Credit Union (CACU) accounts. Error began when I added my business account to same quicken file as my personal account. Different Usernames and password on the CACU accounts. Quicken would crash during One Step Update (OSU) and then I'd get the CC-800 on personal account after subsequent OSU.
Removing the business account from the quicken file with personal account and using fix from "Error Massage When Updating Accounts: CC-800" made error go away.
Business account is now in its own quicken file.
Thought I would share.