You should NEVER call loop(). Period.
if (signal == 49) {
while (blinkers < 10000) {
digitalWrite(ledPinIRC, HIGH);
delay(blkFrq);
digitalWrite(ledPinIRC, LOW);
delay(blkFrq);
}
If a 49 comes in (why the heck aren't you making it easy and testing for '1'?), this is an infinite loop. Hardly a good idea.
What is it you are attempting to do, anyway? What is generating the interrupt? Why?