Did you recently merge your youtube with gmail or any other email account? If you did that, your password would then be the one associated with the email account youtube was merged with. I figured this out the hardway earlier this week.
Yes I think it is somthin like that! I maDe my youtube account with a wildblue account which uses gmail and when I got my droid I made an actual gmail account. However up until I switched droids since my first was broken I signed in fine?? I don't know I'm confused? Where can I straighten it out??
I recommend accessing your youtube acct from a pc or mac, have a password reset and go from there. OR if you know that other password, give that a whirl. Also, my two cent suggestion. Password database app. Having one has saved my bacon a lot in times like what you're going through.