I strictly followed the following instructions, and it was done in 10 minutes:
Version 4.7
Prepare the flash: either shutdown your server and plug the flash into your PC or Stop the array and perform the following actions referencing the flash share on your network:
-) Copy the files bzimage and bzroot from the zip file to the root of your flash device, overwriting the same-named files already there.
-) If present, delete these files from the flash (sorry, you will have to re-enter all your users after booting this release):
config/passwd
config/shadow
config/smbpasswd
-) Reboot your server. Once boot-up has completed, you should see "Stopped. Configuration valid." array status with all disks assigned correctly except for the Cache disk. If you previously had a Cache disk assigned, you will need to re-assign it manually and re-apply any unique configuration settings for it.
-) Carefully examine the Identification strings for each disk. If you see "MBR: error", or "MBR: unknown" for any disk, do not Start the array; instead post your finding in the Forum announcement thread for this release. If everything looks ok, click Start to bring the array on-line. Note: there is a new configuration setting on the Disk Settings page called "Enable auto start". If you set this to "Yes", then upon next server boot, if the array is valid, then it will be automatically Started (this is the old behavior).
-) Go to Utils/New Permissions and execute that utility to change file ownership and permission settings. This is necessary for proper operation of the 5.0 security model.
-) Go to Users page and re-enter all of your users. If you plan on using SMB and/or AFP with either Secure or Private security mode, you must enter at least one user because the 'root' user name is no longer permitted for network share authentication.