Well, if it authenticated then my only guess that you probably were penalized for some reason. Having only index page it is sing like a penalty.
The only way to know exactly is to get the answer from Yahoo.
You may also try to post some question here:
http://suggestions.yahoo.com/?prop=SiteExplorer
Try to put it the way like you have some problems with SiteExplorer and only your index page is listed. Do it very politely and if you lucky maybe somebody from Yahoo will give you the answer.