wow that's unheard of! perhaps you need to build some more links to get the engines to recrawl your website.
Thats the most likely reason, if your listed in the yahoo directory in most cases they use the title and description from there. Theres still no tag to stop this at the moment either.
It is either pulling from the site description from an old Yahoo dir listing, or from dmoz listing. These days google/yahoo/msn are just acting strange every now and then.
I kno of a website which doesnt have the description tag but still the description comes up, on further investing I came to kno that it was pulling in from one of the directories
yahoo is the most strange search engine . i have closed one of my web sites nearly one year ago . it keeps the index of that web site yet
If the description is taken from DMOZ (ODP) then you can change the description to your description. Add this code: <META NAME="ROBOTS" CONTENT="NOODP"> Wait for the crawler to stop by and it should be changed. In case the description is taken from the Yahoo! Directory, then you're out of luck. There is no way around that yet, maybe emailing the Yahoo! guys. I heard there will be a separate tag for that soon, so sit tight.