Thanks for this topic. There's really a bug about downloads detection in the latest version; during rewriting hooking functions I've forgot for one check. So, in this avast build all downloaded files (saved by standard legitimate way) are not saved in the sandbox (which is done by default). All files created/downloaded with different ways are always virtualized, this remains.
Just to be clear: if the mentioned checkbox is checked, it does the following:
- changing your browser's settings becomes permanent
- bookmarks/cookies/history/... are saved on disk
- standard downloads are detected and the files are saved on disk outside the sandbox (this works for all browsers, even if you choose different location - so IE downloaded are detected as well; in fact, this also works for other applications than browsers, run e.g. Microsoft Paint and images will be stored outside sandbox as well)