Mario Kart 7 Communication Error

[Beardy]

I can't seem to play this game online. I've played other 3DS games online and they've been fine, but I always get a generic "a communication error has occurred" message. At most I'll manage a couple of laps, then it'll crash.

I've had a bit of a poke around online about this, and (I'm in no way a techie type) I always find insanely intricate ways of fixing it by fannying about with your router settings or whatever. Anyone know a quick, simple fix for this?