Buddypress Activity Page Works, but Give permission error when set to front page

I'm quite sure this is a permission error or something on the server, as it seems to be unique to this site only.

Just setup a buddypress site for one of our clients and everytime we set the activity page to the front page (via settings - reading) we get an error stating no permission to access / not found.

The activity feed however works by itself and works on my install on my server.

Would something like this be created by permissions or has anyone experienced something similar?

Thanks,

George