The trojan name is less important than the infected file name and its location, this helps us to better identify it and as you found lots of hits on google.
What was the infected file name, where was it found e.g. (C:\windows\system32\infected-file-name.xxx) ?
If it came during prevx update it may possibly be detecting a virus signature file that isn't encrypted, that is also why the file name and location are important. Check the avast! Log Viewer, Warming section and this information should be recorded.