Limited Administer section

Hello,

I am setting up my first site with drupal, but all of a sudden my Administer Section has become restricted to a few options only. I also am not able to create any new content anymore.

In the Administer Section I only have the following options left (see image attached):
- User management: Acces rules
- Reports: Available updates
- Site Building: Blocks
- Site configuration: Actions, YUI Common Settings, YUI editor settings, Administration language

Going to Content management through the navigation, it leads me to the Content management page which tells me: "You do not have any administrative items". When going to Acces rules, I get the message that there are currently no acces rules. There is no option to create new acces rules or anything. The Available updates report tells me everything is up to date. The Site configuration options and the Blocks configuration seem irrelevant to this problem.

When clicking on the Create content link in the navigation, I get a blank page with nothing but a title. Through a link I added to my calendar view, I can jump directly to the creation of a new event, but that page only shows the title and the introductional header with the user guidelines on how to fill in the submission form. The submission form itself, though, is completely absent.

This sudden change occured right after I was experimenting with my calendar view. I was adding the calendar as a block to the right sidebar of a specific node (to test how it would look on the front page) and in the views configuration I had just put it on week view to see what that would look like, and had deleted the header and footer I had added to the calendar default settings (by overriding it).

All it did yield as a result was the header "May", exactly like in the month view, without anything under it. The header and footer were still showing. When trying to return to the edit page, the browser slowed down to a halt. I tried to refresh the page, which brought me back to the test page on which I had integrated the calendar block. Trying to go to the edit page one more time only resulted in landing on the Site building > Blocks page.

I don't know if experimenting with the calendar view like I did had anything to do with the sudden restrictions to administering my website. I have no idea what the problem is or how to solve it. I was very excited about Drupal and the way it could be learned by trial-and-error and surfing this drupal.org site, but it seems like I have encountered some sort of technical defect that goes way over my head. I'm hoping someone can help me restore my site. Thanks!