IMO, you should rename your plugins directory (and leave it that way till you fix the problem) and change your theme to a default/standard one. Try that for a while and see if it fixes your problem.
Note that the memory error is due to php consuming memory to store WP stuff. 67Mb is a lot already. You can increase it, but IMO it is due to another issue - http://codex.wordpress.org/Editing_wp-config.php#Increasing_memory_allocated_to_PHP