I've done two things today that might have affected this:
1. Installed (and then uninstalled) the google file embedder plug-in for WP
2. update BPS security plug-in.
I've now deactivated all my plug-in's but still can't use the visual editor for posts or pages. Also change edit the permalinks. Everything else seems fine.
Any ideas please - or can you refer me to a WP programmer who could fix this for me as I'm not a techie. Thanks!