To clarify the situation for anybody who might care, the Mac stores files normally, but also stores a "resource fork," information about what we would normally consider the file itself (the "data fork") so that another Mac can guess what to do with it without needing to touch the file (the UNIX/Linux approach) or guess based on the name (the Windows/WWW approach).
The default compression programs figure all the world is a Mac, so they happily bundle up both forks for every file. Everybody else sees a folder called .DS_Store with a bunch of crud in it named after the real files. Normally, this is OK, because a person can just ignore it, but some of the comic applications...weren't exactly built robustly. So they see the folder, jump in, and say, "hey, these look like they're supposed to be pictures, but I can't understand them. Something must be wrong."
There might be a setting provided by Apple, but external programs are usually written with portability in mind, so they'll skip the resource information.
