Jim, it may be because Mudcat is done in Cold Fusion - a database interface of sorts where pages are created "on the fly" and aren't indexed or indexable in the same way as normal HTML (that's just a guess though - I'd have to check to see how it affects search engines).
Google works by page rank - each page is given a "weight" depending on how many people link to it - the more a page is linked to (again weighted, depending on what sites link to it), the higher it'll appear in the search results. Interestingly, Google caches the whole HTML source for the page - most other search engines only index metatags and links and titles etc. That's why, if a page no longer exists, Google can still sometimes provide you with an old page from the source they have cached. Contrarily, however, depending on when they update their caches, you could get a search result for an old page and when you click on the link there's a new updated page without the info you want.