A couple of thoughts -
Only Adminstrators can perform system restore.
Also, Antivirus utilities can affect whether your system can be restored to a previous point.
If a restore point contains an infected file because the utility is not set to clean the file within the restore point, or if an infected file has been removed from a restore point by an antivirus utility because it could not be cleaned, System Restore will not recover the computer to this partial or infected state. If System Restore could not restore your computer to a previous state, and you suspect that one or more restore points contain infected files or have had infected files removed by the antivirus utility, you can remove all restore points from the System Restore archive by turning off System Restore and then turning it back on.