I only use the Avia Layout Builder on the homepage (currently), but in building the homepage last night, I found that I can add elements, but not edit the majority of them – or rather I can edit but not save them at all – for example the Promo Box just will not save the changes that I make to it
1) Please try to increase the allocated php memory to 128M: http://codex.wordpress.org/Editing_wp-config.php#Increasing_memory_allocated_to_PHP
2) If 1) doesn’t help deactivate all plugins and check if you can save the elements. If yes a plugin conflits with the theme and you can activate the plugins one by one to find the culprit.
3) If 2) doesn’t help try to re-upload the latest version of the theme. I’d also suggest to re-download the theme files from themeforest again to be on the safe side (corrupt files, etc.)
This happened overnight – no new plugins added – no changes made to core theme files
First suggestion has solved it though