Do you have a 7100 device? They are the most problematic!
Try backspacing and re-entering the text. If that doesn't work it's because sometimes the auto-correct feature gets carried away. I know I had problems registering some software for that reason. You could: change your passwords or logins to begin with upper case or numerals; or, create a note and cut and paste the text on to the field. That's how I got around the problem.
You may be able to turn auto-correct off, but I never tried so I don't know if it's feasible or not. Hope that helps.