I had 2 user accounts with seperate passwords.
One account "standard" and the other "administrative" My "administrative" account does not accept the password. My "standard" account works okay.
Have I been hacked?
If you see the message "The user profile service failed the logon", see this:
First you say the account vanishes, then you say the PC doesn't accept the password for the account. Which is it? If the password was known good, but now it's not, something has gone wrong and it may be an indication of malicious intent. If the password is being accepted, but the logon fails for another reason, then it would be very premature to assume malice.
Answer #2 was the best reply. Yes, it was a malicious infection.