Here's what I would do at the store if you brought it to me... (bare with me I want to get into crazy detail here).
First I'd verify your Nook is running the current software and that the Nook Color's memory had been partitioned by tapping the nook button and choosing "Settings". From that menu I tap "Device Info". If your Nook Color shows anything other than a number of MegaBytes out of 1.00 GigaByte under "Other Storage Available", I'd talk to you about partitioning the memory and explain that you'll loose your sideloaded content and your progress in your games (back to level 1 of Angry Birds). I'd let you know that this will take some time because it also rolls the OS back to 2.0 and we'll have to update the software too. I'd also make sure you know the password for your B&N account because we'll have to reregister.
If we don't need to partition your memory (I've seen it fix things I was surprised it fixed) then I'd check the software version by tapping "About Your Nookcolor". The current package is listed in the thrid entry down and as of today (6/15/2012) it should be 1.4.2.
If your software is up to date I'd go to the web browser by tapping the nook button and choosing "Web" then use the menu on the far right of the URL bar (it looks like 5 little dashed lines with a tiny downward pointing arrow). Choose the last option on that menu "More Options". From the "More Options Menu" I'd choose "Settings".
From the "Settings Menu" I'd clear the cache and the cookies, and suggest we clear the history, form data, location access and passwords too just for good measure.
Then I'd go to the apps menu by pushing the nook button and tapping apps. Then I'd open the email app. I'd ask if you knew the password for your email account and if so I'd delete the account in question by selecting the second button from the left and choosing "Accounts" from the pull down menu. I'd check the box to the left of the listed account and then tap the garbage can on the far right at the top.
I'd then double tap the nook button to get to the home screen and preform a soft boot on the nook by pressing and holding the power button, ignoring the dialog box, until the nook shuts down.
After about a 5 count of being off I'd turn it back on. Have you re-enter the email information using the email app and hopefuly that would clear up the problem.
If it doesn't we'd talk about doing a hard reset and I'd have to explain about loosing sideloaded files and resetting your progress with Angry Birds! We'd do that by turning the nook off then pressing the power button and the nook button at the same time. I sometimes have difficulty timing it right even though I've done it a bunch of times but if you release the power button after a couple of seconds but keep the nook button down you should get a yellow screen for a split second and instrustions on how to proceeed.
This is probably overkill, and simply doing soft reboot might clear it up.
