The Mersenne Twister RNG was updated by the original author in 2002, because of a small problem in the seeding procedure, which was that the most significant bit of the seed was not well reflected to the state vector. Read http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/emt19937ar.html for more details.
The version implemented in Boost is the original 1998 one, which contains the problem. The attached patch implements the new seeding procedure, which uses something different than the linear congruential RNG to initialize the state vector. I haven't identified the new procedure to match any generator already implemented in Boost, so I just wrote it there (please correct me if I'm wrong).
The problem we have here is that the behavior of our mersenne twister is now part of the C++ Technical Report 1, we should really report this as a defect, and get it changed there if this is indeed a problem. John.