Right, had a fiddle.

Can some people try it while I brave the gales and nip round to the chinese take away?

Yeah, that got me thiknking and was the basis of the fiddles I did before I went out.

:(

I think it's one of the following:

Network (i've updated all drivers, checked cables, rebooted router etc.)

Hard drive (i've updated drivers, defragged, turned off real time scanning in AV etc.)

A creeper in the code has blown up.

I'm going to launch a new world and see what happens.

I don't know if/how you can do that :|

I tried a new map, and I tried it with my old router (so no online access as the new one is router and modem built in) to rule out that too, and it was the same.

I have /no/ idea, so I'm choosing to assume something went wank during the install. I am currently nuking it and reloading Windows (fail)