betterzip [still] strangely seems unable to expand some .sit files. granted, it is very rare, but i have come across about half a dozen .sit/stuffit archives which betterzip can not process. i think i mentioned something to this effect in a comment on your blog a while back. one example which is always retrievable is this one;

http://www.gaianmysteryschool.com/timesurfer/TimeSurfer.sit

anything strange about this file?
have you discovered any particular reasons why [rarely] some .sit files are incompatible with betterzip?