Even if you get into the right profile, I've had to enter my existing password and <u>repeat it</u> in the 'confirm' field up above where you type signature text at times when I edit my sig line. I don't know why, but doing it often works.
I also get random error messages if 1/the photo doesn't work or 2/there is too much text (which generally happens when they mess up the photo and generate hundreds of characters of html code.) There is a character limit (255) so that could be the problem too- if you are editing and trying to add too much, hitting save/enter/whatever it is, and THEN getting the password error.