Rig Edit Squashing Hands? I've been working with this rig I made for a long time using it for a variety of characters and it has never given me this problem until now? It keeps its shape until you parent it to the mesh and then it squishes the hand and deforms it improperly. 

This is what it looks like when its not parented, and as you can see, something on the rig is not right in the fingers? 
 

And this is the result of parenting the mesh to the rig which obviously doesn't look right compared to the first.
 

Any advice is great because rigging is not one of my favorite things to do although it is necessary for character animation.

.Blend
I would try and place the armature correctly within the mesh before pairing. Then when pairing select 'automatic weights' to initialize the 'painted weights' for each bone. Then it is useful to go into 'Weight Painting Mode' select the problematic bone areas and try to paint the weights so that each bone only effects its nearby mesh.

This is a great series about rigging. The episode I've linked to is about Weight Painting. Highly recommended.
https://www.youtube.com/watch?v=G3gIN4dJYw4

*It looks like your middle finger bone is deforming the mesh of the other fingers.

Good Luck!