Hi, Are you using spybot. If teatimer is running then this could be the problem causing. I had once upon this problem and did away with total uninstallation to have my restore points. If not, the adware or something, may be present in the extended drive partition in the system and just total format is the only way around.Please, my advise to uninstall program is by using revo uninstaller, a good and safe, (will not pop up message like do you want to delete this file, system could be using it ) and then reboot to find whether sr is working.
If the problem still could not be found, pl use this microsoft instructions to have sr functional
To start System Restore using the Command prompt, follow these steps:
Restart your computer, and then press and hold F8 during the initial startup to start your computer in safe mode with a Command prompt.
Use the arrow keys to select the Safe mode with a Command prompt option.
If you are prompted to select an operating system, use the arrow keys to select the appropriate operating system for your computer, and then press ENTER.
Log on as an administrator or with an account that has administrator credentials.
At the command prompt, type %systemroot%\system32\restore\rstrui.exe, and then press ENTER.
Follow the instructions that appear on the screen to restore your computer to a functional state.