Why is the scan stuck on 83%? It's been at that point for at least 6 hours?

Hello  and Welcome to the Webroot Community Forums!
 
Try
Stop the scan, restart the PC, run a new scan.
 
or
 
In some cases this issue may be solved very simply by booting the computer in Safe Mode with Networking
and running the program there. 
 
Safe Mode with Networking loads a default video driver at a low resolution or screen depth which may cause your software and desktop to change appearances. To access this mode of Windows please follow the steps listed below:
 
1. Restart the computer.
 
2. When you see the black-and-white Starting Windows bar at the bottom of the screen, repeatedly tap the F8 key until the Windows Advanced Options menu appears.
 
3. Use the Arrow keys to select Safe Mode with Networking and press Enter.
 
4. When you are asked to login to Windows please login to your account.
 
5.   
       Open SecureAnywhere and click the 'cog' beside 'PC Security'.
       On the Scan & Shields tab, select Custom Scan.
       Select deep scan from the Customized Scan Window and Click Start Scan

6. After the scan has run then restart your computer to see if that has fixed the problem.
 
If this does not helps, please Open a Support Ticket 
 
Hope that helps - let us know how things go.