Indexed pages went from 10,400 to 437-- why??

Hi;

I'm new to this group and to sitemaps. I first uploaded my sitemap Dec
26th. Within a few days, my account showed 10,400 pages indexed. It
then dropped to 437 pages (out of almost 120,000 on the site) and has
not bounced back. Anyone else have this problem?

Thanks,

tracy
www.artsmart-online.com