Well, here is another page which refer to similar problem you are having. But you may try the way they got to get over it, as they say:
-login using Ubuntu Classic
-Go to the system menu. Select preferences, assistive technologies.
-In the Assistive Technologies Preferences window, select "Enable assistive technologies" and then click on "mouse accessibility."
-In the mouse preferences window, select the accessibility tab. Check the box for "initiate click when stopping pointer movement."
-Close those windows and return to the desktop. Right click on the gray panel At the top of the screen and select "Add to Panel..." Select Dwell Click Applet from the list.
-The dwell clicker should now be functional. Hover over the mouse icon on the panel applet to enable/disable it.
-It is now possible to login using Unity, and the dwell clicker still works, but the applet is not displayed. Additionally, if I close the click selection window, I have no way of choosing a click type.
Here is the link to where I got this from.