When a specific computer can't connect to certain sites, but others work fine the first thing to check are the other computers on the network. If they are experiencing the same symptons, then check gateway/router, or ISP end of things. If a specific machine experiences the symptoms only then check out the following suggestions: 1. Clear temporary internet files from browsers options. 2. Run adware/spyware/malware scanning and cleaning utilities. 3. Disable security software such as firewall, anti-virus, content filtering(i.e. norton, mcafee, ect..) 4. Try a different browser or reinstall/repair the current one (internet explorer) 5. Run a system restore or reinstall windows if all else fails.