Itunes password bug

My mac has recently shut down due to the battery dying, quite normal, right? Well each time I have to sign into my iTunes again to make the little icon quit bouncing, of course. The problem is that each of these times itunes will not accept my password, it doesn't say incorrect username or password, it just simply won't do anything but disappear and then pop up the same sign in box a second later. So, I consistently have to change my iTunes password.