Shader import error: Out of memory, but not really

I have around 30 shaders, each with two multi-compiles, and four shader LODs, all referencing a single cgInc file.

In the last week or so, I've noticed a recurring issue with the shader importer.

When I import the shaders, I get the following error with 30-50% regularity:

"Shader error in [path and name of shader]. Out of memory"

I'm running a 16GB Mac laptop, with Unity 4.6.8p3. Also, Unity remains stable after the error appears, which I assume would rule out genuinely running out of memory.

I can reduce the cgInc file to the following and still reproduce the error. Which I guess rules out shader complexity as a cause:

 #include "UnityCG.cginc"
 
 struct appdata
 {
     half4 vertex : POSITION;
 
 };
 
 struct v2f
 {
     half4 pos : POSITION;
 
 };
 
 
 v2f vert(appdata v)
 {
     v2f o;
 
     float4 lPosition = v.vertex;
     o.pos = mul(UNITY_MATRIX_MVP, lPosition);
 
     return o;
 }
 
 fixed4 frag(v2f IN) : COLOR
 {
     fixed4 final_color = fixed4(1,0,0,0);
     return final_color;
 }

I've pretty much run out of ideas on this one. Are there any known fixes for this?