Uno r3 Works until I Login (OS X 10.10)

I'm running OS X Yosemite and I've got an Uno r3.

It appears that I get a tty.usbmodem showing up in my /dev list. In fact, I can communicate with the Uno. I can upload sketches, etc.. The problem is that it appears to be rebooting in 5 second intervals on the dot. For example, if I upload the basic blinking sketch, it will reset on the 5th interval and start back over. I notice the 13th pin led blink three times and then the blinking starts over again.

I noticed that when I reboot my mac, the Arduino will operate normally. The blinking will remain constant and it will not reset. When I login to the Mac, it begins its vicious reset cycle. I'm at a complete loss.

I've updated the drivers, uninstalled, reinstalled, rebooted, etc. Like I mentioned before. I've got a 5 second window to do my testing until the Arduino resets. I'm at a total loss. I've searched for hours on the internet and I can't seem to find anything that reflects this issue.

-Phil

Just use Serial programming . Let us know in screen shot.

Dispaly the counter for ever 1000s .

int a=0;
void setup()
{
Serial.begin(9600);
}
void loop()
{
a++;
Serial.print("value of a is:");Serial.println(a);
delay(1000);

}


Put me snapshot ; just check how long it can print data??