There is a bug in OpenCV 2.0 packaged in Ubuntu Lucid (10.04), since the function cv::FAST(), declared in the headers, is not actually exported in any library, so that's the reason for the following error building MRPT against that version of OpenCV:
../../lib/libmrpt-vision.so.0.9.1: undefined reference to `cv::FAST(cv::Mat const&, std::vector<:keypoint std::allocator=""> >&, int, bool)'
collect2: ld returned 1 exit status
1. Remove opencv packages, download opencv sources (2.1 or above) and build them.