freeze on train

My MacBook 17" with Yosemite froze on the train today.

I was travelling and it froze, I could get it to be ok at a train station.

I assumed it was the wifi signal so I switched off wifi.

The same occurred again as we left the station.

A guy in a nearby seat was also using a macbook but his was working.

The menu, top bar and app stopped working.

Why should his work and not mine? I noticed hi macbook was tethered so I'm still assuming it was a wifi issue, but that seems to make no sense.

I travel back tomorrow, any ideas?