Robin2:
The normal Arduino oscillator frequency is 16Mhz and the data sheet suggests an error of either 2.1% or -0.8% at 57600 baud.Are you running an Atmega 328 at 1.84.... MHz? Does the Arduino IDE know that that is what you are doing?
I have never had any problem communicating with my laptop at different baud rates using 16MHz and 8MHz Atmega 328s.
...R
I know about normal arduino and no, of course I'm not using 1.84MHz, this is a frequency from the datasheet.
2.1% is a lot.