I've only ever seen this error occur when some kind of old save data (such as from the demo or another version of the game) is being used. It will likely happen at the start of every route, as that is when the journal first loads. When Renpy goes to call the journal up, if it's using old data, then it won't be able to find the journal and the game will break.
My only recommendation is to start a new game and play through everything again and try to load those scenes to see if it still happens!
~Esh