There are no "official" versions, because Ben is no longer active and several groups are making releases. I seem to recall someone made a fix to beta 5 and released it as beta 6. I suppose the closest thing to official we have now is videotools.net.
VirtualDub reports when it detects that an emms instruction has been omitted. It probably means one of the filters loaded in your AVS is MMX optimized but the author has forgotten to reset the multimedia state. It's not likely in VirtualDub itself because Avery never forgets stuff like that.