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Question: Is the unit completely dead, or do you still have access to the files? I assumed since you didn't say it was dead that you still had file access. If that is indeed the case, one other thing you can try is to reset the unit to factory defaults and reconfigure manually, don't read in a saved configuration. That cures many ills with this box.
I had the same issue where I could not log in to the admin page, it would cycle back to the login even though correct credentials were entered. Removing and replacing the BT client solved it for me. I now run the box for months at a time without restarting and I can access the admin options.
Or just assign static IP addresses to your devices including the NAS.
Did you try restoring to factory defaults and reconfiguring? How about removing any add-ons as a test? I'll bet one of those measures will restore normal operation, because there are tons of people running the plain DNS-323 with that firmware.