This probably isn't the answer you're looking for, but you could try using a 3.5.0 kernel.
I had a similar experience to you when using 3.19.0 kernels on as Asus X453M laptop, but no such problem when using 3.5.0 kernels.
(Unfortunately I would really prefer a 3.19 kernel, because it allows me to get two-finger scrolling which I can't get with the earlier kernel.)
$ apt-cache search linux-image-3.5
$ sudo apt-get install linux-image-3.5.0-54-generic # or whatever
When your machine reboots, you will need to go to
Ubuntu (Advanced) and arrow-down to reach the 3.5.0 kernel.
If the older kernel satisfied you, you could make grub select it automatically.