Can often fix by pasting this line into wp-config.php file (or adjusting if already present)
define( 'WP_MEMORY_LIMIT', '256M' );256M is recommended for wordpress, less will often cause issues for some plugins etc.
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.