It's possible that something has changed purposely.
Can you be a bit more specific as to what exactly you cant do.
For instance, can you do the following:
Switch to the Eyedropper tool.
Click in a paragraph
Move to a new PARAGRAPH.
Click and that paragraph changes its character and paragraph attributes.
If you can't do this, you may have to trash you ID preferences. If you can, we'll go to the next task.