Personas error - screen output area too small

Hi all,

  I am consistently getting this error when i make changes to a persona and from then on i can make no more changes and have to restart the screens from scratch.  Some of these screens are really basic and i am not making huge changes but i can see no logic to the cause of the error.

is there anything obvious anyone can think of that i am doing wrong?  We are on 3.0 SP01.

Thanks

Sinead