Just to interject here... I recently did a fresh install of FC5 and I too thought I had no mouse once the desktop loaded. However, the mouse was working. It was just invisible. Please make sure you that you really don't have any mouse activity. You can do this by moving your mouse around the screen. If you go over one of the menus, the tooltip will pop up. If that happens then the mouse is there. You just can't see it.
The remedy for me was to edit xorg.conf and add this line to the video card section:
Option "HWcursor" "false"
Evidently, there's some problem with FC5 auto-detecting certain mice in conjuction with newer Nvidia video hardware.
Hope this was helpful to you.