Do you have the same browser on laptop and desktop? I've been getting the same thing recently but I think that I have worked out why it is happening to me. On my desktop I'm using Opera 7.23 and on the laptop Firebird. I use the Opera wand to fill in my password and it seems as though it automatically sends it (I'm sure that it didn't before) so if I click on OK or enter (or whatever the Yahoo button is called) it sends it twice and I get "password incorrect".
Don't know if that helps you at all but at least you know that you are not alone :-)