It could very well be a false positive. Submit the file to virustotal http://www.virustotal.com/xhtml/index_en.html If avast is the only one detecting it, then add it the exclution list. There are 2 lists. On access, left click the"a" icon, click on the standard shield provider, customize button, advanced tab. On demand, you can do that from the simple use interface or right click the icon and select program settings. Post back your results.
