This is strange. From what I've heard and my experience, a quality USB<>UART chip from FTDI is the way to get a reliable serial connection. I've used mine to talk to a Dreamcast at 1.5 mbaud. FTDI is the one with the good drivers (both closed and open). Controllers like the PL2303 are nothing but pain. Of course, if you get counterfeit ICs (and they are common), you will probably have a bad experience. Buy carefully.