Don't know if you still have the issue, I recently started having the issue (seemingly out of no-where); just thought I'd post my fix. I have SuperAntiSpyware on my computer (I'm not advertising for them, just don't want anyone to go through all the long hours I went through), there's a tool in the "Repairs" section called "Repair broken Network Connection (Winsock LSP Chain)". As the program states, please use with caution. Once I ran that, I had to restart as it did something in the registry. Once it came back up, BAM, fixed; after about a month of trying to fix it... Hope this helps someone...
Edit: Btw, it says it's for Windows XP, I used it on Windows 7 ultimate 64-bit and it worked no problem.