Can the people who built it for Windows 64-bit, explain a bit how they've done it?
Have you used mingw? mingw-w64?
Did you have to update the default packages?
Did you install every needed package by hand (configure, make, make install)?
Any other details?

Thanks.

Edit: just found this https://bitcointalk.org/index.php?topic=240894.msg2597100#msg2597100