Why does my computer have dementia?

Lately, my computer is incredibly slow to load programs but only some of the time. When I go to load Fluther, for example, sometimes it will chunter and chunter and I’ll get a message “Downloading Proxy Script” and then “Resolving Host.” Later that day it may work perfectly fine and then again, it may crawl.

Here’s what I’ve done so far – rebooted it, of course, although I generally leave it on all the time. Cleared browsing history and cookies. I thought it might be a problem connecting to the network so I rebooted the network which runs on Verizon Fios and restarted the wireless router.

I also ran a full scan using Microsoft Security Essentials and nothing showed up as a virus.

I’m running Windows 7 and generally use Chrome as my browser.