after going thru the System Restore process,and any message stating "Cannot restore the computer to an earlier restore point, no changes have been made to your computer" pops up, try the procedure listed below to restore its functionality.
Right click [My Computer] [Properties] then click on System Restore tab.
Put a check in the box for Disable Restore on all drives.
Click apply, then Reboot your PC.
After the system reboots, navigate to the System Restore tab and turn it back on. Click apply. Navigate to [System Tools] [Restore...] and choose [Create a Restore Point]
Provide a name for the new restore point. Try and restore the new point just created. It should work properly.