Admin pannel does not refresh

I just updated my blog to 1.5 and the admin pannel does not refresh any of the data. If I activate a plugin, it is activated but in the admin pannel it says it is not. If I add a new plugin or a theme they are not shown in the list of the plugins. Whatever I do I cannot logout. My admin login is always logged-in. And the dashboard does not update.
Also the awaiting moderation page does not update. I have a comment, I approve it, I can see it on the blog, the awaiting moderation goes to (0) but when I click there, the comment is still sitting there.

Could you explain this?

Thank You