I think it might be a mix of too many plugins, too much bot activity (you wouldn't believe how much spam I get to my site), and the host arsing about.
Was planning on moving to a dedicated server I have in the US, but as this has somewhat come out of the blus will see now about moving RC and some other Irish sites over to Michele's new VPS. I really need to immerse myself more in the server side of stuff anyway.
I need a new site for RC also... one that I can get some time to post on
Actually - need a new me...
 Note - replied at same time as richard [/edit]
I'd say he means that there are limits on the hosting he has and he reached them OR his site is taking up too much of the cpu on a shared box and others sites on the server were suffering. I'd say WP can handle the traffic but if your host has automatic suspension for going over your limits, you get hit with those messages. A real pain.
Camino, just make sure your host is scalable and if it gets really busy, it's not that difficult to move to VPS or Dedicated hosting.
Needless to say, your site must be doing really well Richard.