I have the exact same symptoms ever since updating Jessie on my languishing rpi. Stopped working the moment after post-update rebooting.
One way to confirm it isnt a hardware issue is to include the command lcd_rotate=2 in your config.txt file.
In my case, and I presume in yours, the affected half of the screen will rotate as well. This means it must be a software / formware issue. I found a few other relevant topics when I first started looking into this a month or so ago and will post the links when I find them. Some of the users report these fixes working while they do not work for others (including me
I’m surprised there aren’t more people with this problem, but the affected group sure would appreciate a fix.
I’ve even tried Fresh installs via noobs to no avail. My solution is a not working touchscreen and check back here periodically praying for a new/revived thread on this topic.
Any help is greatly appreciated.