Windows 8.1 issues: 

Touchpad gestures stop working after sleep in Windows 8.1 

This is a common issue after the 8.1 update.
After you put your laptop to sleep and wake it up , the touch pad seems to stop working.
if this is the issue, if you're facing this issue follow these steps :

1. Check for the latest version of the touch pad driver if it's not up to date then please do update it.
2. If the drivers are updated then , go to the desktop , and once the desktop appears , left click on the desktop  and  then press <ESC> key thrice.

This seems to resolve the issue for synaptic touch-pad for DELL laptops.{maybe for other touch-pads also}

 
Hope this resolves the issue.