|Well first of all you should disable the hot corners. |
Go to System Preferences > then Click on the Expose & Spaces > then Click on the Expose tab and you should see the four corners.
Next to each corner there is a drop down menu. Just click on all of the drop down menus and select the "-".
Now at least it won't activate the hot corners.
Now for why your mouse is acting up. Try cleaning your mouse lens. What kind of mouse pad are you using if any?
If it's a laser mouse then some surfaces will not work with it.
Blow at the bottom of your mouse where the lens is. Maybe some dust got in there.
Also, try using the mouse on another surface. Does it still do the same thing?