Hi, this thread is pretty old, but I have the same problem here described, and I cannot find a fix.
Specifically, when I try to allow access to "Everybody" on a shared folder, it works for another english-OS pc, but not for a spanish Vista OS. The same happens with shared folders on the spansh OS, since there I cannot give access to "Everybody" but to "Todos", and then the english-os pc cannot see the shared folder.
It is only my problem (ie, am I doing something wrong?), or is this an OS limit? And is it possible to sort it?