I'm unsure of how the D3D shader compiler / effect system works when specifying just one address mode in the sampler state.
Here, you're just applying the CLAMP state to AddressU without setting AddressV or AddressW.
Does the effect compiler output any warnings/errors?
Searching through MSDN I found this: http://msdn.microsoft.com/en-us/library/windows/desktop/bb509644(v=vs.85).aspx
Though this doesn't really answer that question, it does give an example in "MeshTextureSampler" for trilinear sampling.
(Also, I assume the duplicated "gPointSample" is a copy/paste error?)
Hope this helps
Additionally, since you're sampling in the geometry shader, ensure you're using the correct texture access method: http://msdn.microsoft.com/en-us/library/bb509700%28v=VS.85%29.aspx. I.e Load(), SampleGrad() or SampleLevel()