icloud - there was a problem loading the application

I keep trying to log into ICloud.com to update my calendar, notes, contacts etc. I get into ICloud ok but as soon as I click on any of the icons (calendar, notes, contacts etc) I get the whirling wheel which runs for a few seconds then stops. It remains frozen for many seconds and then I get the the message - There was a problem loading the application. I get the same message whichever application I try.

My Ipad and IPod are happily syncing away but I can no longer do large changes via the web site which I found easier.

It also make me feel uneasy that I can't access the applications.

Can anyone help?