Hy Gus, it´s a pleasure to meet you. 
Here goes my test case:
- I used two boards, FEZ Cerbuino Bee and FEZ Panda II.
- Connect the GND Pin between the boards.
- Connect D0 of Panda II to D1 of Cerbuino Bee
- Connect D1 of Panda II to D0 of Cerbuino Bee
- Now the UART1 (COM1) of Fez Panda II are connected to UART3(COM3) of Cerbuino.
6)Open a Serial port in both boards using the following parameters:
FEZ PANDA II
SerialPort UART = new SerialPort(“COM1”, 300, Parity.None, 8, StopBits.One);
FEZ Cerbuino Bee
SerialPort UART = new SerialPort(“COM3”, 300, Parity.None, 8, StopBits.One);
7) I´ve set the error handler to the port on Cerbuino using the following code:
UART.DataReceived += new SerialDataReceivedEventHandler(UART_DataReceived);
8) I´ve tried to send data from Pand II to Cerbuino, and i recieved a error on the error handler:
The exception was of a type {System.IO.Ports.SerialErrorReceivedEventArgs}
There was no message or inner exception, just the event type and a code:
EventType = Frame
m_error = 0x00000004.
So… it happens too when i´ve tried to use a 600bps baud rate (Same error code and EventType).
And just one time in 1200bps baud rate (maybe it´s been sporadic this time) .
So, my application uses a 300bps baud, and the Panda family is on legacy state.
There´s a workaround to use a low baud rate on Cerbuino family?
Thanks a lot!!