See this from AVG: Please rest assured you are still protected by AVG even if you have already upgraded to Firefox 6.0. The AVG Active Surf Shield component is still checking all data and will prevent you from accessing malicious content even though search results verdict icons are not available temporarily.

I had chatted with AVG Tech Help. They have confirmed that AVG Safe Search is still NOT compatible with Firefox 6 yet, only the AVG Toolbar is. They are working on it right now and will release the next update once it is done.

Here's the information from AVG forum, read the last post by DrDemento:

http://forums.avg.com/ww-en/avg-free-forum?sec=thread&act=show&id=170885#post_170885

Thank you silkphoenix and Andy.c!