I have been logged into musing for more than 12 hours but I haven't faced such issue. I can think of two things that may have caused this. One of which would be a musing bug and the other is that there was a problem with your browser interacting with the site. 

It is unlikely that it was caused by a bug cause if that was the case, then it would have affected  many other users as well. As for browser cache, you might want to restart your browser and then clear cache to see if that helps.