My own site can't be accessed

Hello all, It's not a Trinity problem (although it happens in kmail), but as I know there are some experienced people on this list, maybe someone can give me a hint. Since yesterday I can't connect kmail to my main mail server (the server of my own website). I can't send either, I can't connect to the website, I can't connect to it's cpanel, I can't ftp either. I *can* connect to the internet, I get mail from another website, it's really only "my" website. I use spamdrain as spamfilter and spamdrain can access my mail. So does gmail. My handphone can read my mail over data from the very same pop3 server. The provider says from his point of vue everything is working. I've reset the modem and the router. It's not my machine as every machine on my local network has the problem. What, on my local network, could block access to only my website (the provider's site is accessible)? Firewall is activated but nothing has been changed yesterday. The fact that only *one* site is having problem makes me think the problem is at the hosting site, but... I'm really puzzled. Thierry