Scratch Neutron

Why am I now being asked for my password when I try to buy lindens ...and then I cant purchase? I get a message that the password I entered doesn't match the one in their records . Yet I haven't changed my password and use it to login to my dashboard, marketplace and inworld. I have cleared cache... and tried to purchase lindens like I have been doing for the past two years. I have rent to pay !!!!! Help !!!!