Mike wrote: "I don't think it would be a good idea to try to install 2 versions of Flash."
There's nothing wrong with installing both versions of Flash... I have been using both for years.
The active-X version enables Flash in Internet Explorer.
The plugin-version enables Flash in most other browsers, such as Firefox and Opera.
Users need to be aware of this, and install the version(s) of Flash appropriate for their browser(s).
Apparently, based on your issue, avast coordinates itself with the Active-X version of flash.
So if would want to use Avast and Firefox, you need both flash versions: the activeX for Avast's statistical display, and the plugin for Firefox.
I would not classify this as being a bug.