Phew, 'good' to see I'm not the only one
Thanks - rolled back to 136 and everything worked straightaway. Went back to 137 and things were ok initially, but I think this was because the states had been retained from 136 - as soon as I forced torrents to update by doing 'force recheck' they stopped downloading. All was ok again when I went back to 136, so something is definitely wrong with 137 in certain scenarios