Web Browser Difficulties

A few weeks ago, I started noticing that my Google Chrome browser would stop working at unusual times. When I would try reopening Google Chrome, It would fail immediately. I decided to use Mozilla Firefox instead, and that worked for a while. Now, I am having difficulty using both browsers. Sometimes even a reboot of my computer will not solve the problem. I have scanned my computer with McAfee, and it says that I have no viruses. I cannot figure out what is wrong.