Animation scale problem

Wat my problem is, is that i rigged a model up with armatures and used vertex groups instead of wieght paint or other things. anyway wat the problem is that when i go to rotate a armature (or bone) it scales the mesh smaller the closer u get from turning it to 180 degrees from its origanal state. I have the vertex groups set to 1.000 if that has anything to do with it. Also the mesh does rotate but it still scales.

plz help

Can you can post the .blend file to give people a better idea.