This past week Adobe released an update to Flash Player 9, dubbed "Moviestar". As of build 220.127.116.11 there are issues with ExternalInterface causing SWFAddress not to function correctly in AS2 projects. The release notes on Adobe Labs says that ExternalInterface has been improved, and after some tests it has been determined this is the source of SWFAddress failing silently.
So, just to be clear, the bug only affects ActionScript 2 (AVM1) websites and applications - those written in ActionScript 3 (which uses AVM2), such as Flex applications, are immune to this bug.
This was first brought to my attention through a blog post on the issue, and He also submitted a bug on Adobe's website so they would be aware of the issue. I suggest if you are also experiencing problems that you submit the bug as well, as the more reports Adobe receives about a bug the faster it will get solved.
If you have any further questions, the Sourceforge email list or forums is a great resource. I also suggest reading Rostislav's blog post for more detailed information.