Yahoo Replaced Domain with IP address

How do I fix this?

[mikey158]

After the last index update which resulted in a deeper crawl of my site (yea!), I now am listed two different ways in the index, under the domain name (1 page indexed, ranks well for targeted keywords) and under the IP address (100 pages in index, none of which rank).

I have not found ANY sites linking to the IP address. To complicate things ... this server and IP address host 4 sites (IIS using host headers).

Also, I might add that the other SE's have it ok with all four domains.

Any thoughts on how to fix this?