Automatic draft not functioning

Recently i updated tp 2.8

And now there are few things that not functioning at my end. Everything is working fine everywhere except if I am adding a new post or editing a post.

1. When i press the ‘screen options’… nothing happens. No options are displayed as a scroll down effect.
2. No scroll down effect happens in the main menu.
3. I cannot add tags from the right side thingy in add post and edit post. Even after clicking “add tags” button, wordpress is not remembering any tags.
4. wordpress is not saving the content automatically into a draft.
5. After writing the stuff, if i click the “preview” button, it opens a new add post page instead of showing my written stuff in my blog.

And this is not a browser specific problem. All this prob are going on in firefox as well as internet explorer. Can anybody suggest me what could be wrong? I think wordpress is clashing with some plugin… but i am not sure of it.