MacBook Pro :: Its Mail Keeps Rejecting My Yahoo Password

I have my yahoo email account set up in my mac Mail. Recently I keep getting this message saying that Yahoo.ca IMAP server "imap.mail.yahoo.com" rejected the password. My password is all correct and I checked "Remeber this password in my keychain" but it still doesn't work. This message keeps poping out everytime no matter whether Yahoo is trying to receive new emails or not.

I originally thought it was a probelm from Yahoo, and I had emailed them this problem, and they said they had solved this issue from their end even though I kept telling them my password is still not accepted. The strange thing is that I think I could still send and receive emails (although not sure if I am receiving all the emails since the message kept poping out and that my yahoo keeps on going processing mode and then in the end a triangle with exclamation mark just appeared)

Another strange thing is that I have another Yahoo account on my Mail, yet this one never had simialr problem like this before. It is alsways this particular account I have that is having this problem.�I tried changing my password, logging in Yahoo from their website making sure the POP setting has checked. Still didn't solve my problem

I have tried going into my keychain to verify and repair my password from Keychain First Aid. But no problem was found.I have also tried deleting my account from Mai Preference and re-added back on, still doesn't work.The first time this problem had happened to this account, I ended up deleting it from Mail and added back on and it seemed to work, however this time nothing seems to be working.

Info:Mac Pro, Mac OS X (10.6.8), Mail version 4.5