Vertex shader (GLSL) strange behaviour; Does not draw - opengl

Question

I'm trying to implement skeletal animation using my vertex shader. I pass the indices and weights of my vertices as attributes, and upon drawing I pass the animation matrix for every bone as an array to my shader.
Now for some reason when I add the calculation to my shader my model disappears. Even if I do not use the result of the calculation ANYWHERE in my shader, it causes my shader to disappear. No errors are thrown.
I've done a lot of testing and found out that it only happens when I try to access animationMatrices[60]. As far as I've seen any index below 60 works. This is wierd however since I only have 53 bones in my model.
To illustrate, the following code doesn't draw anything:
#version 330
uniform vec3 light = vec3(10,2,8);
uniform mat4 modelmatrix;
uniform mat4[64] animationMatrices;
attribute vec3 a_tangent;
attribute vec4 a_boneIndices;
attribute vec4 a_boneWeights;
out vec3 lightVec;
out vec3 eyeVec;
out vec4 test;
void main()
{
vec4 newVert = (animationMatrices[60] * gl_Vertex) * a_boneWeights.x + gl_Vertex;
vec4 vertPos = modelmatrix * gl_Vertex;
gl_Position = gl_ModelViewProjectionMatrix * vertPos;
eyeVec = normalize(-vec3(gl_ModelViewMatrix*vertPos));
gl_TexCoord[0] = gl_MultiTexCoord0;
//some more stuff here but not important
}
If I comment out the newVert line, my model shows up.
So, if I remove or comment out this line the shader works fine (or change the index to something lower than 60):
vec4 newVert = (animationMatrices[60] * gl_Vertex) * a_boneWeights.x + gl_Vertex;
As soon as I re-introduce this line nothing shows up anymore even though newVert is not used anywhere in the shader.

Answer 1

Assuming modelmatrix is not an identity matrix, you are transforming your vertex incorrectly.
First from object-space to world-space:
vec4 vertPos = modelmatrix * gl_Vertex;
And then from (what is supposed to be) object-space to clip-space:
gl_Position = gl_ModelViewProjectionMatrix * vertPos; // vertPos is in world-space!!!
You need to stop doing this, or isolate your View and Projection matrices.
Possible solutions:
1. vertPos = gl_Vertex;
2. gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
3. gl_Position = projectionmatrix * viewmatrix * vertPos;
Considering a few lines below it, you compute something called eyeVec:
eyeVec = normalize(-vec3(gl_ModelViewMatrix*vertPos));
You probably should not be touching vertPos at all, the only way this shader will work properly is if vertPos = gl_Vertex (potential solution #1).