Next step is to check for viruses. A few things to check first is such as the host file. Its locatd at c:\windows\system32\drivers\etc. Open it with Notepad. there should be nothing listed after th example. If there is, delete it and save.
Then downloda and install CCleaner. Run it to kill out anything in the temp files. Then download and install Malwarebytes, Super Anti-Spyware and Microsoft Security Essentials. Run them all after installing and updating.
Hopefully if there is anything blocking your internet then it will get them.