> What versions of MRI are you using [as in compile--mingw, etc.]

> are you using pre built gems?

From the original post's DETAILS section, my setup below.  The MRI is RubyInstaller (mingw) RC1.

The FFI 0.5.3 gem is the prebuilt mingw binary.  It also segfaults with the prebuilt mingw 0.5.4 gem.

Thanks, Jon

> ruby --version

ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32] 

> gem --version

1.3.5

> gem list ffi 

*** LOCAL GEMS *** 
ffi (0.5.3)