Having the same problem, I have tried all their suggestions (empty trash folder, deleting unsychronised notes, clearing cache, and so one...). None effect ! So I reported the bug to support team, very reactive.
It seems they have not really working solutions, except uninstall /reinstall application, what i have done and it works.
But, this is not satisfying, because you may lost many notes/changes and need to review the parameters.
I have asked them to solve the bug as soon as possible, because it's a problem on Evernote reliability.
Let's see the results...
