how to add an exclusion

Suddenly my HP Photosmart printer has stopped printing my documents. There is nothing wrong with the printer per se, it will print a test page, I can print from emails and pages from the internet. Whenever I try to print a document it comes out as a blank page, I have exhausted all avenues, help sites, diagnostic checks say everything is working properly. I tried downloading another word processing programme and it still doesn’t work. I had a pop up from Avast saying it blocked a programme and I could add an exclusion but I don’t know how to go about doing that. Can someone help me resolve this problem because I’ve been trying for over a week now with no solution

Exlucion http://www.avast.com/en-eu/faq.php?q=exlusion#searchForm

Avast FAQ http://www.avast.com/en-eu/faq.php
FAQ videos http://www.avast.com/en-eu/faq.php?q=video#searchForm

I had a pop up from Avast saying it blocked a programme
What program ???