There is a bug report here, even patch if it's still usable:
This is irritating, I import DBF files on daily bassis. Can you make option to select character set once and checkbox "Always use this character set" or something like that.
I spoke to Muthu (the patch author) about this while we were in Nuremberg. Let me take another look at this to see what was still needed to be done with the patch, as I remember saying that there was still some work that we needed.
I should give this to Muthu.
Ported to libreoffice now. Should be fixed in 3.5.