My programmes on my computer can't connect to the internet?

[shadow]

I first noticed this when I tried to upload a video to YouTube via Camtasia. I kept getting the message "Cannot connect to internet" or something similar. I believed this was because I had failed to update it. It still won't work.
Around a week later, I downloaded Steam, and this wouldn't connect to the internet either; I assumed this was just because something was wrong but I couldn't find a solution on the internet. This isn't working either. I think the error code was either 130 or -130.
Finally, today Skype won't connect. Which is ridiculous, because Skype has being working since I got it nearly half a year ago, was pre-installed on my laptop, and worked only 2 days ago. It just says it has failed to log me in. I've got the password right and everything else right too.
Extra Information: I run Comodo Dragon web browser and my anti-virus is also Comodo. I recently uninstalled McAfee per recommendation from a tech-savvy friend; this came pre-installed. If you need to know anything else to help, please contact me. Thanks in advance
EDIT: My firewall is fine, it lets the programmes through, so it must be something else. Thanks anyway Warlock...

[Warlock]

Firewall. Mo matter how many programs you uninstall if your Firewall blocks it, it's blocked. Search in the start menu for "allow a program through firewall" Once you are into the settings, click change settings and unblock all needed programs