DIGITS: Machine restarts when I use AlexNet or LeNet

I am new to deep learning and been reading quite a few papers recently (Sorry if I posted it in the wrong section/forum). I have installed Cuda, cuDNN, DIGITS, etc. To get used to DIGITS interface I run googleNet for a classification problem. Everything is okay. But when I use LeNet or AlexNet the entire system restarts. What I mean restart is everything went blank back to DOS and the machine starts up again. I suspect the problem is because AlexNet and LeNet are deep networks and require more memory? is that right? can someone help me to diagnose this problem please. Or maybe I didn't install some required software correctly?

By the way I'm on Linux 16.04 (again I'm quite new to this OS), Cuda 9 and cuDNN 7, Nvidia driver 384.98

I really appreciate your help. Thanks a lot eric