Message body empty

Ever since 1.8 (and latest 1-x-dev), when I try to send an email, I am getting the following error:

Error sending e-mail from my@emailaddress.co.uk to "=?UTF-8?B?TUVESVVNIEFFVlVN?=" <my@recipient.co.uk> : Message body empty

On Krumo Log, Body is indeed empty:

Body (String, 0 characters )
$...['Body']

But the contents I am expecting are appearing fine under "Alternative Body"

Alternative body (String, 2125 characters ) boundary="d07cfd20d2f928ba0d56e58ad432c6b0a184a...
boundary="d07cfd20d2f928ba0d56e58ad432c6b0a184a4a00"
Content-Transfer-Encoding: 8bit


--d07cfd20d2f928ba0d56e58ad432c6b0a184a4a00
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
 ETC ETC

In short, the problem seems to be that view send is putting the body into 'alternative body', and nothing in 'body'.
This may be an error in my configuration, or is it because of a change since 1.7 ?