Pastor Andy, it's probably a space related issue.
Please go to the 'Settings' page and tap on 'Device Information'.
There will be a row there that says
Storage for B&N Content.
And another that says
Storage for Other Content.
The first shows how much is available for things you buy from B&N like Apps. The second shows how much is available for other content like movies and music you move from your PC to Nook.
Most Nook Colors only have 1 GB allocated for 'Storage for B&N Content'. So that fills up quickly.
The solution is
I Figure out which apps and books you aren't using. Archive them.
Important: Archiving deletes ALL data. So please make sure you do not archive any apps that store data like Calendar Apps and that you don't Archive any apps that save game progress like Angry Birds.
Only games and apps you don't use at all any more should be archived.
II) Go to Settings > Device Information and confirm that you have freed up space for 'Storage for B&N Content' row.
III) Restart. This is necessary.
Power Off: PRess and hold power button for 20 seconds.
Power On: Press and hold power button for 4 seconds.
IV) Now try to install again.
This should fix the issue.
The long-term solution, if 1 GB of space for B&N Content is proving too small for your needs, is to go to a B&N store (helps to call before hand and check if they can do this, some stores can't).
There they will repartition your Nook's hard disk. This will require redownloading everything and you'll lose data and progress etc. However, after that, you'll be able to store more things you buy from B&N.