Why would my mouse pointer be jerky when it can't get a signal from my router?

I've seen this issue with my wireless mouse, as it is in a similar frequency range to wifi - I resolved the issue by moving my wireless mouse dongle further away from the wifi antenna at the rear of my PC.

I'm confused as to why a wired keyboard would suffer the same fate though... something you'll have to come back to if this resolves the wireless mouse issue I guess?!

It's probably related to the networking and networking drivers in windows. I've noticed that on some machines when windows is busy with the network it can affect the mouse and launching apps as well. Everything becomes jerky.

Make sure you have the very latest wireless networking drivers and ensure you've done a windows update as well and see whether that helps.