Since more people have asked this, I have extended my CUDA cubic interpolation code with 1D cubic interpolation as well. You can find the updated code here: http://www.dannyruijters.nl/cubicinterpolation/
A working CUDA example that also contains 1D cubic interpolation can be found in the cudaAccuracyTest sample in the examples subdirectory in CI.zip.
For those of you who are more interested in a SSE approach, I have some working SSE optimized multi-threaded cubic interpolation code (albeit in 3D, not 1D) in the referenceCubicTexture3D sample in the examples subdirectory.
edit: The cubic interpolation code is now available on github. The 1D cubic interpolation code is here.