Dell inspiron 15r SE

If I keep a key pressed and then try to left click the left click doesn't work. The cursor moves without any problem but left click doesn't work when you keep a key on the keyboard pressed.

It is quite notice able in games like call of duty where you need to keep "W" key pressed to move forward and  simultaneously Shoot using left click on touchpad.

This didn't use to happen. Yesterday I upgraded my OS to windows 8.1 and since then i am having this problem. I am currently downloading new drivers to see if the problem solves.