What are you using to send data to the board?
Also, the serialRead() and serialAvailable() functions are deprecated in favor of Serial.read() and Serial.available(), so they don't really get tested. Can you use the latter functions instead?
I'm using my linux box to send serial data over USB.
I see that HardwareSerial.cpp simply wraps serialRead(), serialAvailable() and the other funcs directly, so there's no difference using Serial.read() instead of serialRead()... (Since I write everything else in C I don't want to use the C++ Serial object)
Isn't it strange that the RX led don't even light up when I send to the arduino and the arduino isn't sending anything? Should this led light up even if the arduino isn't actually handling the data? If so, the problem must be that my computer doesn't send anything unless it recieved something...