I naively pointed to by x84 R build on windows 7 64 and it appears to work fine.
R version 2.12.0 (2010-10-15)Copyright (C) 2010 The R Foundation for Statistical ComputingISBN 3-900051-07-0Platform: x86_64-pc-mingw32/x64 (64-bit)
It is however compiled on my machine from source, so I don't know if that helps
Great project!! Wiped out months of work, done and still to do!