Very strange problem

My server reponses to ping or traceroute fine, the load is low and normal but noboy (in different countries) can access normally the domains/mail on the server.

I checked dns, bind, named and all is ok, i dont have a new firewalls or something like that, i didnt take new action to cause this.

Yesterday all was working perfect and today you take up to 5 minutes to acces a simple domain with a basic html page (if you dont get before a time out response)

When i connect via ssh, if i execute a command like "ps -fea" or "top" i get desconnected the server do nothing.

I informed to my server provider (theplanet) and they checked the server and the network and they say that all is ok.

But my problem still there and worst, I supposed it was my isp, but i had a lot of calls from clients in different cities and countries with different isps.

I dont know what more to do.

Any suggestion?