Can eliminate congestion - it'd be worse at peak times.
Can eliminate noise as at least the primary cause - it'd have a bunch of packet loss rather than the spiky latency as packets are lost due to the noise. Noise also causes excruciatingly slow downloads.
Do you have anything else that might be consuming a lot of upstream bandwidth on the connection? Something running P2P software perhaps?
Any chance of the upstream power levels? Any T3 timeouts?
I'm leaning towards the Superhub going faulty or high utilisation of the connection. Reboot it, see if that helps. There is a bug in the Superhub 1 that causes weird latency issues but those usually escalate and then stay awful rather than coming and going.
Try switching off wireless temporarily and run with nothing connected for a few minutes, see what that does.