This is probably not the problem, but just in case, are you sure that a Calendar is selected? It is possible to have no calendar selected, and so you will not be able to view any appointments, it will also go through the motions of letting you save appointments, but of course it saves it nowhere (it should really tell you at this point there is no calendar selected, but it doesn't, I'm going to file a bug on this, as I just did it).

Also when you uninstall, I don't believe it deletes the .gpe files in your home directory where files and setting are stored, so the state of having no calendar selected would still exist.