connection issues with 3 arduinos any suggestions? I have 3 arduinos that I want to program on, all of them with their own cable and I have tried to connect them to my laptop on several different usb ports, my usb ports work with mouses so that's unlikely to be the problem. However I just cannot connect to them they just don't appear under /dev/ttyACM* and the arduino IDE cannot find them either. I'm running ubuntu 14.04 any suggestions for finding out what is likely to be wrong with my system or the arduinos? 

For some odd reason they now all appear to be seen as /dev/ttyACM* but they now all give me a 

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00


error

Anybody have any idea how to fix? The arduino's do not have any wires in them except usb (nothing in reset or any other pin), I'm on ubuntu so the drivers shouldn't be an issue? And pin 13 flashes when I reset the arduino.
it's been a while but a long time later I found that the cable I was using was broken. A different cable worked.