Hi,
I've been using an FTDI Serial converter to talk to the ATMega328P-PU on a breadboard.
I kept getting this error occur when trying to upload to the chip, all the wiring was correct, but still would not upload. Using the SPI route, was fine. The chip was functioning correctly and so was the Serial comms. But the chip STILL would not program via the Rx and Tx lines.
Turns out that even though I ALREADY burned the boot-loader, it didn't actually seem to take correctly?
Reburned the boot-loader and all was good. Spent the best part of 4 hours trying to figure this out. I just hope this helps some other poor soul.