itunes won't recognize a valid password

Here's a weird one. (MacBook Pro 2.4G 10.6.2) Tried to buy something on the itunes store, and my password does not work. So, I recover the password. Still doesn't work. Then I reset the password... 3 times. None of those work either.

So, I go to my office computer (Mac Pro 8-core 10.6.2) and reset the password again. Works fine. I can access the itunes store or anything else on Apple's site. I take that same password into the other room, and using the MacBook Pro, the itunes store says "invalid user or password" and will not allow me on. Yet, I am still on that computer, using that same password, to log into the forums here... This computer will log into Apple but not into itunes.

itunes support says that since the password is stored on their site, it should work on either computer. It doesn't.

Ideas??

thanks

Don