Google has an option to 'remove url' or 'remove from cache' option - what is the procedure for Yahoo to remove a search result (an outdated page or nonexistent page on your site perhaps) or to delete a cached page?
try robots.txt my experince shows that yahoo is quite fast robot, and hopefully, your page will get out of index next time slurp hits it. you can ping that page or something to attract slurp i think
I have not encountered problems like this.. But there's one thing that i really hate about indexing pages in yahoo cos one of my sites is still not appearing in Yahoo... Google and Bing already indexed my Blog Site...