My Windows 8 laptop will do this every now and then and rebooting fixes it.
However there are rather hidden settings in the Control Panel> Mouse which are worth checking - there's a little 'gear' when you click on the options, easily overlooked and you can change various less needed things including scrolling behaviour.

I noticed when mine was playing up that several things here were greyed out - until it was rebooted.
It's probably a driver issue which will eventually be fixed. It seems to be on the latest here but that's something else you could check.