With my Window 7 64 bit computer, when I try to open multiple attachments, it will open some, but not all attachments. I typically get three attached to a single email, and CS6 will usually open two.
OK, In Thunderbird, I select Open All, and it will usually open one or two of the JPGs, but then I get a Download Error (example), .../AppData/Local/Temp/+O3YpIHo.jpg coult not be saved, because the source file could not be read. Try again later, or contact the srver administrator.
I use the same procedure in CS5 and it works without error.