I had a similar problem with a different website, where I lost a function on the site. It was there one day and not the next.
I logged out and logged back in... no help.
I logged out and rebooted the PC... no help.
I logged out, cleared out my browser history (hadn't done that in months), rebooted, logged in... problem solved.
Just coincidence? Don't know... just know that a chance shot seemed to help.
Only bad thing was every application that required a log-in needed to be re-done. It was fun remembering which user names and passwords went together.
