In post 5 I asked about the PC port, and you said that the same thing happened on another computer. ?????

As far as the programmer software reading back correctly, all I can say is it happens. I have a PICKIT1 that will read back errors if I use the software that microchip supplied, but mplab does not. Both software work. I would guess in this case the "lesser" software does not have something correct in its receiving side, like a checksum miss calc.

Again, check the signal with a meter. TX will show low (Maybe even a negative value) when idle and will spike anywhere from 2.5 to 25 V+ at transmit. If you have a machine less than 10 years old or using a usb/serial adpt, you will most likely see 2.5 to maybe 6.