http://www.quirksmode.org/bugreports/archives/safari/index.html "If a page calls window.open(), then submitting a form on that page and returning to it using the "back" button causes the entered form values to be lost. (ppknote: Safari has a different bug: it doesn't show the form at all when you go back. This has nothing to do with opening a new window.) Test page http://h1.ripway.com/magicm/ Workaround is included Reported by: Milo van der Leij."
Works in latest nightly.