The AVG Toolbar is now called Secure Search and it can be downloaded from the official website. What you've encountered appears to be something called "false positive", when the antivirus detects an item as being infected while it actually isn't. Technically, the software isn't a virus, but it might contain ads or search add-ons. It could be called being "adware" instead of trojan.
Check all your downloads at VirusTotal service as well (www.virustotal.com)
Official website: http://www.avg.com/eu-en/secure-search
