I was having a problem with V2.0 Beta(not this issue), so I installed V2.0RC, and this very strange things happens. Nothing like this happened in V2.0 beta or previous releases.
I’d start by disabling all plugins and clearing or disabling caching, if applicable. It stands to reason that AT, for example, might cause problems here and there, as the plugin contains similar features as we recently introduced (such as the quick access bar).
It’s an Advanced Themer conflict. If you scroll to the bottom of that right-hand icon list, there should be a icon button to close it. Doing that, I haven’t seen it reappear since.
You see, exactly what I suspected. I’m also sure that Maxime will resolve the conflicts as soon as possible, and that it’ll work in the stable version Pre-release versions are intended to uncover such problems.