bluetooth error ??

I had roughly the following code

void loop() {
    char x;
    int n  = bluetooth.read();
    x = (char) n;
    Serial.println(n);
    Serial.println(x);  
//    bluetooth.print(x);//echo back
.....

note that the last line is commented out, if I uncomment it, I can let my serial terminal on computer echo back what I typed. but randomly I would get the bounced back character to be char 255 (a non-printable char), is this due to some hardware contention/bug that the sparkfun.com SMiRF board can't handle immediate receive and send ?

I had roughly the following code

And you had an exact error scenario. Rather hard to believe.