When I try to delete duplicates in my contacts the next time I open yahoo contact list doubles. how do i fix?

this is not a virus because this appears on any computer i use. it is obviously a yahoo problem. initially when I tried to run the "eliminate duplicates" option a message appeared saying something about a script error that would make the computer run slowly; however, even when I manually delete duplicates the next time i open up yahoo, the duplicates reappear and in additon more duplicates are created. Please advise before I get rid of yahoo completely.