I notice that libopencv2.3-dev provides libopencv_gpu.so. Does this actually provide GPU support or is it a dummy? I have CUDA on my laptop, will it take advantage of it?

I can build an executable that call the gpu function and successfully link to libopencv_gpu. But I can't run it: it fails with the following error message:

OpenCV Error: No GPU support (The library is compiled without GPU support) in throw_nogpu, file /tmp/buildd/libopencv-2.3.1+svn6514+branch23/obj-i686-linux-gnu/modules/gpu/precomp.hpp, line 99
terminate called after throwing an instance of 'cv::Exception'
  what():  /tmp/buildd/libopencv-2.3.1+svn6514+branch23/obj-i686-linux-gnu/modules/gpu/precomp.hpp:99: error: (-216) The library is compiled without GPU support in function throw_nogpu

If it does not, what's the recommended way to get GPU support? I tried compiling and installing OpenCV2.3.1 from source with CUDA support, but I also have to install ffmpeg 0.10, and then I am having problems with different versions of the libraries that I am still trying to sort out...