Black box apears on the right side of the program

[Sorontar]

Black box apears on the right side of the program and everthing is frozen until it dissapears 5 seconds later. I have a feeling it has something to do with project panel having active object. It compresses content of  the rest of the window.

[Mylenium]

This most likely is a dysfunctional script panel, so check what third-party scripts you have installed. Either remove them or find updated versions that are compatible with the latest AE versions.

Mylenium