Onboard LED blinking

I’ve noticed on one of my programs, that every so often the program will stop executing, stay in the state it’s at, and the onboard LED will blink rapidly (many times a second). Does this behaviour signify something?

Thanks!

Which of the onboard led’s

The one(s) that indicate serial transmission ? or the one connected to pin13? (not all Arduino’s has this)

MikMo
http:/www.mikmo.dk

Which of the onboard led’s

Ah, my apologies. It’s the LED connected to pin 13.