I guess I don't know what else to tell you. As I said, the googling I did wasn't definitive but a problem with the kernel configuration was the most common suggestion for the errors you posted. I know a lot has been changing with the linux wireless support stack and it could be that the newer rt73 drivers are changing to reflect the the new wireless stack. One of the things I've read is that the new wireless stack has built-in WPA support, so I suppose that wpa_supplicant may not be needed, at least not in its current form, with the new stack.
So pretty much you can either use the older rt73 driver and wpa_supplicant or the newer driver and its inbuilt WPA support.