I've had my Nook color for about 36 hours. I also had the same issue reported in this thread:
The Store says nothing is available. I tried to check out Apps, but nothing would come up. AFter reading this thread, I did the hard reboot -- held the power button down until the device shutdown, and then held the power button again until the device restarted.
Now the Store and App sections work. I also can view the various departments in the store, which I couldn't do before.
Is this an issue I'll have to deal with from time to time with the Nook Color? If so, I'll return this thing before my 14-days are up. I have no interest in fighting a device every day just so I can browse the store and purchase things.