Comment 6 for bug 1238410

I have nearly the same problem. I have recently upgraded to 13.10 and the invisible-mouse-cursor problem immediately affected me. Basically, I have the following:

 - I have no visible cursor inside LightDM during login
 - I have no visible cursor inside the Lubuntu session of LXDE. Although I can click and perform all mouse activities.
 - For a brief moment, after successful login between the Lightdm and LXDE session, I can see the X server's default mouse cursor. But it disappears as soon as LXDE is started.

I found a rather dumb way of fixing the problem and I have no clue why it worked.

1. Created a new user called 'dummy'
2. Logged out from my default user session (where the mouse cursor is invisible). Alternatively you could do 'sudo service restart lightdm' if clicking the right button becomes tedious due to the "invisible" cursor
3. From LightDM, logged in as 'dummy' - great, mouse cursor is visible here.
4. Logged out from 'dummy' user session
5. From LightDM, Logged in as the default user - voila! mouse cursor is back!

Other tricks that I had tried:

 - sudo update-alternatives --display x-cursor-theme ## make sure it is set to a theme that you have installed on your machine
 - Check ~/.config/lxsession/Lubuntu or ~/.config/lxsession/LXDE to make sure it matches what you have set above

Hope it helps.