Why can't Drupal write to the database after migrate/restore? When I want to do more development on a live site, I usually make a copy of the files and database on my local LAMP install and play with it there.

Now I'm finding that if I copy the database to local using Backup and Migrate or importing/exporting with phpMyAdmin, the local Drupal can only read from the database. It displays pages, but any edits or admin changes don't get saved. No errors, just nothing changes. 

I've tried clearing all caches and running update.php. I'm running the same Drupal version live and locally. If I install Drupal locally from scratch, no problems at all.

What am I missing here... or is there a better way to achieve production/live cloning?
It was a schoolboy error on my part. I didn't have mod_rewrite enabled on my local environment, so clean URLs weren't working.