emacs' ibuffer mode crashes on my machine (Win32, GNU Emacs 24.0.50.1 (i386-mingw-nt6.1.7600) of 2011-01-31 on 3249CTO) when used with complex saved filters. I attached a minimal sample that reproduces the error on a vanilla emacs installation (--no-init-file, built from http://alpha.gnu.org/gnu/emacs/windows/)