I will be lurking to find out an answer - DH and I keep buying dishwasher safe bakeware only for it to go all rusty really quickly!!!
We have even contacted Waitrose to complain about theirs, but they didn't really give us a useful response. They just said that they would ask their manufacturer to investigate(what good is that to us??)
cut a potato in half rub on rust then wash in hot soapy water. I hate to say that if it doens't come off after a few trys at this the bakeware is probably not salvagable. To give you some hope this method (its a kim and aggie) worked on a wok that had been rusty for a year