So, it doesn't seem to be a memoryleak which is nice. It might be a driver issue then, have you tried a clean reinstall of the GFX driver?
The following is one way to do it. There's also programs to help you like http://www.guru3d.com/files-details/display-driver-uninstaller-download.html
This is how you do a clean graphic driver clean install:
Start by downloading your graphic card drivers from here,
AMD; http://support.amd.com/en-us/download
NVidia; http://www.nvidia.com/Download/index.aspx?lang=en-us
Download the one you have and save it on desktop, you are going to need it!
So after downloading and saved it follows these instructions to the letter,
1- press windows button,
2- right click my computer,
3- press property’s, you will get a new window here.
4- in the new window click device manger on your left side of the screen, you will get another new window here,
5- you will see in the latest window a list of devices you have in your computer, click on the arrow beside Display driver and a small fall down menu will show you what kind of graphic card you have.
6- left click on your (graphic card name) so it’s highlighted in blue,
7- right click (graphic card name) and press property’s, you will get a new small window here,
8- in the new small window click on Drivers, you will see the name between the tabs,
9- in the driver menu click on uninstall, you will now get a really small window that ask you if you’re really sure that you want to uninstall you’re graphic card drivers,
10- click ok,
11- after you have uninstall you’re drivers restart you’re computer,
12- after you have started up your computer, click on your graphic card install file,
13- follow the instructions of your graphic card installer, Pick Custom / Advanced and only check off for Nvidia 1- Graphics Driver 2- PhysX System and for AMD card only check off display driver and catalyst control center.
14- when you have Install your graphic card drivers, restart / Reboot your computer,
15- you’re done