When you emerge netscape-flash *before* of any browser who will use it (in my case AMD64 binaries for 32 bits), and *after* emerge this browser (in my case, mozilla-firefox-bin) this plugin simply doesn't work. Workarround: re-emerge after installing that browser (in my case, reemerge after mozilla-firefox-bin).
Well, I really fail to see why would anyone emerge this without an installed browser.