I was playing around with a working Laravel 4 installation and moved everything into a sub folder. Then I decided to not do that and I moved it all back (all via the command
As the problem is related to permissions try re-giving the right permissions to app/storage and all its sub-directories and file.
You can do so from the root path of your Laravel app typing:
chmod -Rvc 777 app/storage
If for some reason this doesn't work, try:
find app/storage -type d -exec chmod -vc 777 {} \;
find app/storage -type f -exec chmod -vc 777 {} \;