Ok, I think the specific issue is whether or not the flash player has transparency support which allows the text below to show through.
The original test Ned added for Linux was to check if the Flash Player version was > 7 on Linux -- which worked.
Apparently the newer version for Linux still does not have full transparency support (for the flash wmode property).
I've tested on my machine and verified that with FF and Flash Player LNX 220.127.116.11 the sIFR is not replaced. I'd like to get some others to test with various platforms and flash player versions before I push this out.
Could some others test this page and note if sIFR works correctly for your flashplayer & platform..?