Login issue after Migrating from PC

Hi. I created an account on my new MAC and then used the migration program under 'Utilities' to transfer user data from PC to Mac. All well and users just need to put in a new password when they log on to the Mac. Apart from one account. This account seems stuck in the 'enter a new password' loop. I haven't entered one but I enter a password, and no matter what I do the screen flashes and leaves me at the enter a password screen. I've tried loggin in as an admin on another account and changing the password but I am told on screen that this will not change the account's login password. Please help as this account is the one that had all my itunes and documents so took ages to transfer. Thanks, Ima.