I recently switched back to using PLA after I got tired of trying to use ABS (warping, de-lamination, et cetera) and I've started having issues with jamming.
My printer is the QIDI Tech (the version with the ATMEGA128 controlling chip) that has been re-flashed with Sailfish ver. 7.1.
The slicer is use is Slic3r.

So, this is what happens:

I load the filament in normally and without issue first. The filament during the loading extrudes out without any evident obstruction.
I then try to print a test piece ( http://www.thingiverse.com/thing:342198 this to be exact) and the HIPS/PLA start without problem. (the little test line at the start is smooth and clean)
I leave the print, and when I check on it halfway through I find that the PLA has stopped extruding.

Above is a picture of the failed print, see how the extrusion became wispy. By the point I had noticed, the printer wasn't extruding at all.
This was actually my third attempt with this print, the first one I stopped to modify some settings, and the second one jammed in a similar fashion (the build plate was also poorly leveled during the second print, which I fixed for the third).

Above is a picture of the first print (still on its HIPS raft). See how much better the print is.
The only difference between this print and the third one's settings is the fact that I turned on the filament cooling fan (as far as I can remember).

Above are pictures of the filament I pulled out of the printer after the jam.

This link is to a ZIP file containing all the pictures of the prints and the removed filament: https://www.dropbox.com/s/95glrp2yg5...shoot.zip?dl=0
This link is to a .ini config bundle file for Slic3r which contains my current settings for PLA: https://www.dropbox.com/s/f2v88z6kbe...onfig.ini?dl=0
In the configuration bundle, untitled is for the PLA and untitled 2 is for the HIPS.