Unable to start steam: To run Steam, you must first connect to the Internet

Solution 1:

As the Steam errors are quite vague, and can refer to a lot of different things, there's not an exact solution. However, the best way to troubleshoot it, is by eliminating various causes.

1. The most common issues can be solved deleting the ClientRegistry.blob file and force Steam to download a new and fresh copy of it.

   The clientregistry.blob is a file for the program Steam. The file holds your registration data for your games. If you delete it the file will be restored and you will have all of your default settings on all games installed (like your name, spray, binds, etc)

   • Go to C:\Program Files\Steam (or the Steam directory that was specified during installation).
   • Locate ClientRegistry.blob and delete or rename the file to ClientRegistryOld.blob.
   • Next time you start Steam, the file will be forced to download.
     
     

2. Another common issue is the update list can become corrupt, this is solvable by deleting the AppUpdateStats.blob file and forcing Steam to download a new and fresh copy.

   • Go to C:\Program Files\Steam (or the Steam directory that was specified during installation).
   • Locate AppUpdateStats.blob and delete or rename the file to AppUpdateStatsOld.blob.
   • Next time you start Steam, the file will be forced to download.
     
     

3. If none of the above work, you should try to start Steam on another computer on the same network, to check for router problems.

   • If Steam doesn't start on another computer on the same network, it indicates that there is a problem with the router.
     • Your router might need port forwarding. Portforward.com is a great site for tutorials on how to forward ports on a lot of routers.
   • If Steam starts on another computer on the same network. It's something with your computer that's causing issue.
     
     

4. If you have a firewall, try disabling it and start Steam.

   • If Steam starts your firewall might be blocking it. If you are using Windows Firewall, navigate to Control Panel\All Control Panel Items\Windows Firewall\ and press the "Advanced Settings" button on the left side. Then press the "Restore Default Policy" as this image shows.
     If you are using another firewall, please consult the firewalls manual to figure out how to restore the default settings.
     
     

5. Some programs may interfere with Steam and it's connectivity.

   • Check your latest installed programs with Steam's list for programs that might interfere.
     
     

6. Some Spyware, Adware, and Viruses also interfere with Steam.

   • Scan your computer for viruses, spyware and adware with an Anti-Virus program of your chose. If would recommend the free version of AVG, if you are in need of a Anti-Virus program.

Solution 2:

The answer to most problems with Steam is to close Steam (shouldn't be a problem for you :P), then go into your Steam Folder (default C:\Program Files\Steam) and delete "clientregistry.blob".

This fixes most login problems, offline mode not working etc, because it causes Steam to re-update to the latest update (should be very quick as it mostly just verifies the files you've already updated).

Solution 3:

I found that PeerBlock 1.1 was causing this issue on my Win7 machine. Disabling peer block fixed the issue for me.