On PowerShell.org, the bar reads both "Login" and "Log In" as two separate entries. It looks like the second "Log In" is what is required to get access to the forums, though even that requires some page refreshing to get the post option to appear. I don't know if other folks are having problems, but it took me a good 10 minutes of poking about with both IE and FF to get the topic post to appear.
While the two buttons are confusing (they're added by separate plugins, and I need to modify one to stop it), they both go tot he exact same URL. So.. they're the same thing.
We have some fairly aggressive caching. This may just be an issue of needing to do Shift-Refresh in your browser. If that solves it, or helps, let me know and I'll see if I can tone down the caching on the forums URLs.
Got the superfluous button to go away, and was able to log in using this Facebook account, and didn't have to do anything funky to see the page change. Do keep in mind the number of potential caches between thee and the server (proxies, etc) and consider if that's a factor for you.