Nevermind – I was able to restore the website from a backup.
Seemed to be working fine even up til the end of last week, so not sure what has happened, but I’ve got sites in 3.42 and 3.5 and Publicize isn’t working in either of them anymore…
Have just checked another WP blog still in 3.4.2 and it’s not working there either, so seems to be a Jetpack problem???
Thanks 360
I actually discovered the problem was that my hosting account was set up for Windows, not Linux. Have changed it to Linux and now all works fine.