why my switch blinking rapidly

Hi,
why lately my switch blinking rapidly so sudden, and my server processor show 100% processing. that couse network slow, and some application fail to load. my only solution is just restart the server, but I think that the worst solution. so pls any body help me what’s going on with my server/network? is this DoS attack? but my server doesn’t contain any web server, or mail server.
thank’s

J Brown.
04/29/04