I have noticed that the RAR plugin does not properly support multipart RAR archives. If you click on the .rar file they open okay, but if you click on any of the parts (e.g. .r01, .r27 etc) then you get a new lister showing the same directory you double clicked from.
I checked for duplicate unrar.dll files, there is only one in the dopus directory and no others. I am on the latest version of Opus (9.1.3.0.3449) and using the 32 bit version on Windows Server 2008. The same thing happens with the x64 version on XP x64.
Instead of getting the contents of the archive in the same lister, I get a new lister with the same directory as the one I clicked in and the file I clicked on highlighted.
The RAR plugin only handles .rar .r00 and .r01 files by default. You can add other extensions to it via Preferences -> Plugins -> VFS Plugins.
If another program (e.g. WinRar itself) is associated with those extensions then you will also need to override their filetype double-click actions. (Sounds like that isn't the case, or has already been done, since double-clicking them is opening Opus and not something else. So you just need to tell the RAR plugin it should handle the extensions.)
As far as I can tell, though, you don't see the full archive when you enter an archive part (other than the first one). It may only show files in (or maybe in & after) that part.
A better solution might be to make double-clicks on the later parts open the first part. If you do that then it works better and you don't have to add any extensions to the RAR plugin either.
To do that, create a new filetype (I called it "RAR Archive Part" in my screenshot below), assign the part extensions to it, and set the double-click action as shown below. (Of course, this will go wrong if the base part isn't called .rar; for some reason some people make multi-part RAR archives that start with .r00 or .r01 instead of .rar.)
