I would suspect virus. If it is virused, there are any number of reasons why you might not have seen any signs before -- it may have recently been infected via an insect vector, for instance, or may have been infected this whole time but is only now showing symptoms. If this is a plant you really like and if you really want to be more sure as to whether or not it is virused, have it tested. Critter Creek Labs is one such place that tests for orchid viruses. In the meantime, if you decide to keep it, be sure to isolate it from all your other plants.