I think Your hard drive is defect or Too many browser tabs are open in your system.
Follow these steps for Browser issues:
1. Restart your browser and try again
2. Update your web browser
3. Turn on restore tabs feature
4. Update Flash and Java
If the hard drive is failing means, computer is slow. Other than too many browser add-ons, too many programs, browser tabs that runs on same time also slowing your computer.
I think your computer affected from malware.