Bruce Haxton pointed out to me that Mersenne Twister and Mersenne Twister Fast still have vestigial references to 0xffffffff (that is, -1) in the seeding code which makes no sense if the values are integers -- it probably just gets optimized out. These references originated from the C code, which couldn't guarantee that integers were 32 bits.
I have committed revised versions of the Mersenne Twister code both in the ECJ and MASON packages. This code has those references commented out. It LOOKS like it's still seeding identically, but I would appreciate some additional eyeballs testing such a core piece of code. Can anyone help out please?