Blender - Difficulty with Cloth Simulation

Hello,  I am hoping to solve an issue that I have been experiencing with Blender's cloth simulation. I've posted about this in a few places now, but I have yet to arrive at a solution. 

As per the tutorial, I have tried using a decimated version of the dynotopo model as a collision object for the cloth. (I have experimented with both an extracted from mask mesh and a decimated mesh of the original model to rule out the possibility of the extracted mesh being the source of the issue.) 

The moment the cloth has been pinned to the model is when things go wrong: the vertices directly adjacent to the pins react as if there is no gravity and stay relatively stuck in place regardless of the settings used for the simulation. As you would imagine, that makes for quite an ugly piece of clothing that I would prefer not to drape off my character like a discarded plastic bag. I have made sure that the vertices aren't intersecting the collision mesh or each other, so I'm 99% sure that they are not the cause. 

I tried replicating the problem in a separate .blend file by running the same cloth sim on a three separate objects: a cube, a sphere, and a simple dynotopo mesh. I used the same pinning methods (both with and without the animation of the pin group via shape key) and, despite having similar conditions, I could not replicate the problem. I think there might be some condition with my actual .blend file that is causing the issue, but, to be honest, I'm not sure how to figure it out at this point. 

(I also tested various collision boundary settings and I could only achieve an aggravated version of the original problem, so no dice on that one.)

I have attached a google drive link below to the most current version of my .blend file, in case anyone would like to take a direct look. Any help would be much appreciated, thank you!

https://drive.google.com/file/d/0B7DNn7VakmOfbl9XbnVkSjNjdVU/view?usp=sharing