those are called artifacts. Generally they are related to a GPU that is either overheating or underpowered. Just because you can't feel the heat doesn't mean its not there. As a matter of fact if your laptop is not blowing warm air out of the vents on the back or side (wherever the exhast vents are) that is probably an issue where the fan isn't doing its job.
Unless this thing is a netbook that is passive cooling.
You can try new drivers and see if the issue subsides, but if it doesn't I would get it back to Acer ASAP to be looked at.Drivers for Acer