First I created a package-folder inside the taskManager, which probably resulted in some kind of error.
Then I created a package inside the folder, and added a task inside the package.
When trying to save, the taskManager froze up, and I was no longer able to do anything else, but to close down Firefox.
After re-opening, I tried to create the package in the Own-folder, but received attached error when trying to save the package with one task.
Now it seems that I can't create packages anymore, they are not appearing at all. And for some reason, the folder I created in the first step, now appears twice inside Own-folder.