When in MSN search, I provide a site:www.example.com, where example.com is a domain of mine, a good portion of the returned results list my URL with no cache or meta tag description. These pages don't ever come up in searches either.
Have these pages been banned by MSN ? Is there a likely cause or scenario that might cause this ?
The Site: query is an atypical query. As such, what you are seeing are possible pages you have redirected among other reasons. If your intent is to show these pages in regular queries, I suggest verifying the pages are crawlable, have unique title and description tags and have readable content.