It's a very faint noise, and I can't be sure were it's coming from...and I'm not entirely clear on the difference between a click and a pop. >.< I uploaded a video to youtube:
You can hear it between the 1 and 2 second mark on the video.

It has been several prints since I last aligned, but it seems to be extruding just fine, though it would be hard to tell the difference since the clicking is very intermittent. Single click/pop every thirty seconds or so. Location during click seems to be random, but I was going to realign on the next one anyway. I've also upped the temp back to 115 and the speed is lower than it was when I wasn't having the issue, and I'm still getting it at the same frequency.

Thanks for all your help and advice guys, it's much appreciated.