Effects window is not working properly

Yesterday I experienced something very weird. You know there is this window where you can choose effects. Yesterday this effects window was completely bugging. What i mean by that is that I was not able to open the folders inside of this even though the rest of Premiere Pro worked completely fine: I could play the video... Sometimes this effect window disappeared randomly and after 5 seconds it was back. I don't know what the reason for this is, has anybody an idea?