In the "Projects" dock the context menu "Manage Packages..." works fine when the menu is opened by clicking on a project. However, when using it from the top "Solution XYZ" node it is broken. The "Manage Packages" window will open but any attempt to Add a package results in a "Object reference not set to an instance of an object." message displayed at the bottom of the dialog window and the package not being installed.
I don't remember whether it was possible to install packages on solution level, only ever used it on projects directly. Is this menu item even meant to be shown on this level?