Computer problem

[Barquentine]

I recently cleared out my cookies, deleted temp internet files, cleared browsing history and did a scan of my hard disk with my virus protection software.
Since then - when I try to log back into my YouTube account I get the 'Internet Explorer cannot display the webpage'.
Also - on GumTree - when I went to post an ad. the security words (Captcha) you have to enter to prove it's not spam were blank - there were no words for me to enter!
Also - when I tried to deactivate my Facebook account - again the Captcha security words were blank so I can't deactivate it (I was able to on my office computer instead).
My home page is Google - and in the top right corner it says 'Sign In' - but again I get the 'cannot display webpage' message.
I've tried the things it tells you to do under 'more information' on that warning page - but nothing seems to work.
Everything else seems to work fine. Anyone have any clever ideas what this could be? Many thanks.

[ChuckFickens]

Shouldn't think the two things are linked TBH...

Try disabling your firewall and security software temporarily and see if it works then. if so then it's blocking certain sites..

If it still doesn't work then you may have a malware infection that is redirecting some sites, so try running a full scan with malwarebytes.

[Barquentine]

Thanks Chuckfickens - tried switching off both firewalls - no difference.

I can't see reference to 'malwarebytes' in my AVG scanner - could it be referred to as anything else - 'anti rootkits' for example? It also has an 'advanced settings' box where you can define file type extensions for it to look for? thank you.

[Giggsie]

http://malwarebytes.org/
download and run this