Thanks all for the solutions. I had reverted to a dial up but the box isn't in the same room as my phone point. I was running an extension once a week to update. Not very elegant!
I have resolved the issue. I don't know why, but the default Gateway Address had somehow reverted back to it's default (192.168.1.1). I've changed it back to my router address and it seems to be OK. Anyone come across this?
Automan - I use Virgin Media as my ISP.