I have been unable to withdraw Bitcoins to the address 1DN6ZttogE7eoKFGT3CQqZNDzZREucVmKD

I have used this address many times before, but last time I tried it, I received the error "Invalid BITCOIN address!!!".  I also receive this error if I attempt to change the address to any other address, and it reverts back to the address I have always been using.