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