Further, when I use C-x,C-e to manually evaluate the custom-set-faces line in my .emacs I get the following stack trace:
Debugger entered--Lisp error: (error "Undefined color" "unspecified-fg")
internal-set-lisp-face-attribute(default :foreground "unspecified-fg" #<frame
emacs@devrs005.snc1.facebook.com 0x135f180>)
set-face-attribute(default #<frame
emacs@devrs005.snc1.facebook.com 0x135f180> :stipple nil :background "unspecified-bg" :foreground "unspecified-fg" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil :slant normal :weight normal :height 1 :width normal :foundry "default" :family "default")
apply(set-face-attribute default #<frame
emacs@devrs005.snc1.facebook.com 0x135f180> (:stipple nil :background "unspecified-bg" :foreground "unspecified-fg" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil :slant normal :weight normal :height 1 :width normal :foundry "default" :family "default"))
face-spec-set-2(default #<frame
emacs@devrs005.snc1.facebook.com 0x135f180> ((t :stipple nil :background "unspecified-bg" :foreground "unspecified-fg" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil :slant normal :weight normal :height 1 :width normal :foundry "default" :family "default")))
face-spec-recalc(default #<frame
emacs@devrs005.snc1.facebook.com 0x135f180>)
face-spec-set(default ((t (:stipple nil :background "black" :foreground "white" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil :slant normal :weight normal :height 140 :width normal))) t)
custom-theme-set-faces(user (default ((t ...))))
apply(custom-theme-set-faces user (default ((t ...))))
custom-set-faces((default ((t ...))))
eval((custom-set-faces (quote (default ...))))
eval-last-sexp-1(nil)
eval-last-sexp(nil)
call-interactively(eval-last-sexp nil nil)
One more detail: I'm (ssh -X)'ing into the linux box from a Snow Leopard Mac running X11 (XQuartz 2.3.4 (xorg-server 1.4.2-apple45))