Well... That's strange. If others in the house are disconnected at the same time, I'd have said it's down to the internet, but if you're saying it's fine then I'm stuck o.o ~ Try resetting it anyhow, shutting down your computer then rebooting it.
I had a somewhat similar problem in my house where the internet would anonymously cut off at a specific time of day (Mostly 5am but hey ho). We had to contact the network and have them look into it, you may have to do that to if it comes to it...
If that doesn't work then try changing the rendering systems from OpenGL to Direct3D9. (I swear that is said on near enough every help thread) xD.
Well, Good luck.
Sorry I couldn't have helped much more... But I'm sure others will pick up areas I've missed. <3
~Nym