Ridiculous Issue

I have a class with a member function like this

void CMyModule::onON()
{
Serial.println("CONNECTED!!!");

}

The sketch compiles without errors, but, at the time of upload it, the communication hangs, what forces me to open the task manager and kill the avrdude running process. The ridiculous thing is: if I remove or comment the Serial.println("CONNECTED!!!"); line, the sketch uploads OK.... Now the funny part: I have another method like this:

void CMyModule::onOFF()
{
Serial.println("XXXX WHATEVER");
}

There is no problem with this line...
Now.. total size of the sketch in bytes? 10678 on an ATMega ADK board....
Any suggestions, ideas are welcome... This worries me because it's just an small, simple test which it's expected to scale up
Thanks for your help

There was an issue with one of the bootloaders that caused it to enter command mode when it encountered three exclamation points in a row. So, quit with the excitement, and just none or one, not three.

After all, who'd be crazy enough to put the same punctuation mark more than once... ?

After all, who'd be crazy enough to put the same punctuation mark more than once...

Me???

and me!!!

Thank you very much for your support!!!!
(And me again...)