I agree with Simon - latest info suggests an Adobe CC-2014 issue. Reading those linked Forum postings does not give one confidence in the state of QC at Adobe - so many bugs reported. While a bit OT, if valid it does make one wonder why. Once they have us on the subscription tread-mill, it would seem a win-win for them and for us to make sure the changed features work properly before releasing updates.
Yes, they have a QC issues and their "tech" support" also has issues. I pointed out 2 weeks ago, that once you updated Adobe CC 2014, bridge no longer would open images into photoshop layers in CC anymore. It still opens files and browses them fine. If you try, it just que's them up waiting for you to open CC 2014, unless you reboot. Adobe's answer was "just uninstall Adobe 2014 CC". IMO stupid answer as bridge should see the open version and go from there, not que up waiting on CC 2014 to open.
One answer I received from this forum was "I can't understand why you still need CC", this is exactly why. Things like this, that can totally stop a workflow. I use adobe's photomerge often if not daily and had not seen this issue on CC 2014, but I also only updated it last Friday. Like Wayne points out, there is no way to get a earlier release of CC 2014, once you update. I have a image of this drive I can fall back to where I still have 2014 CC non updated, and I guess I will fall back to that. Currently CC 2014 has trouble with even the most basic photomerges, ones from a tech camera where the back is moved, so the files basically just line up, besides the need for exposure blending, which is where it's failing on my system.
As I stated before I don't think they changed anything at all in the photomerge function as they are the same as in CC, but they obviously changed something in 2014 CC that effects it.
I also realize it's hard to test all features etc on a new release and how the effect current features, but this is par for the course with current practice.
Paul