When the system freezes and you need to hold the power button to shut down, there is a chance that the storage will not mount correctly on the next boot.
This is often caused by data that should have been written to the storage ending up in the folder that is used to mount the storage.
On reboot, since the mount point folder is not empty, the system will automatically create a new mount point and keep the user unaware because this is not visible from finder.
Use terminal to look in the /Volumes folder using these commands :
Look for something that looks like storage_1
OS X has mounted the storage to this new mount point (storage_1) and this still shows as Storage in finder, but underneat the real path is /Volumes/Storage_1
This confuses managed media because it is configured to look at /Volumes/storage
Here is a simple procedure to repair this condition:
In Disk Utility select the storage device and use the unmount button to unmount it.
In finder, move the /Volumes/storage folder to the trash
In Disk Utility, use the mount button to mount the storage again. The mount command will create the /Volumes/storage folder on the fly.