Publish post returns to edit.php page (list of articles)

For some time now I have noticed some issues when publishing posts (such as blank list of categegories when trying to load the new post page or “send to approve” instead of publish button).
Today I got this new error:
– I entered some text in the post-new page, I pressed publish and then stopped the browser, because it was not responding.
– I pressed publish again, the progress bar of the broswer showed 78% loaded, and then the page reloaded and instead of displaying the regular published post is opened this page: mydomain/wp-admin/edit.php.
– I checked and the post was eventually published but the admin behavior wasn’t the expected one.

I don’t think it’s a cause of any plugin, I haven’t changed or upgraded anything in quite a while now.

I’m using 3.0.1, the romanian version and I always use the latest stable version of Firefox as a browser.

Any idea what might have happened?