Have you taken a look at your log files? You should go in there, and make sure that slurp is still visiting your site. If it is not, that can mean there is a problem! I looked at your site, and I can't see any other reason why it wouldn't be working. You have 773 incoming links from yahoo which is good. I would check your log files, you can also go to this page to check Yahoo and google ranking http://www.prsearch.net/index.php or you can go to http://www.devppl.com/msnbetarankings.php to see your new msn search beta rankings.

Here is a good article on the new beta. It seems to be a lot like google was in the good old days. In other words, number of links are important, as well as title and anchor text.

http://www.titan-seo.com/NewsArticles/MSN-Beta.htm

There are also some good articles here on getting ranked in general

www.titan-seo.com/index-2.html