Right click on the red M by your clock and choose check for updates.
Let it update and try to scan.
Since you done the system restore .The Dat file of McAfee might not be updated properly So, please try to run the McAfee Virtual Technician to fix the issue use the following link to run the program.
Could you please let us know if you are able to scan the computer using McAfee ??
McAfee Online Community Moderator