I had to sign up to this forum simply to give Escaping a massive thank-you for posting this solution. After having two web designers shrug their shoulders at the way around the 'sorry, your last action could not be completed' problem that we started to experience I thought I'd sit down with Google and a beer to see if I could muddle may way through and up this post came.
I’ve got absolutely no programming experience and you've allowed me to fix our site; thanks again.