Same for me too, though I’m not using that theme. I’m using a custom built theme.
There’s another thread on this (http://ww.wp.xz.cn/support/topic/plugin-regenerate-thumbnails-stopped-working-error-msg?replies=18), but no real solution as yet as far as I can tell. Very frustrating. Anyone got any ideas on a fix for this?
Thanks very much for your help and advice. I’ll do as you suggest and post back here when everything is done.