[Plugin: W3 Total Cache] error message about wp-content directory

I have not been able to figure out why I get this error message (I’m pretty new at this, so bear with me). I recently moved my site from one URL to another and have been updating my settings in my theme, plugins, RSS feeds etc, but I don’t know what to do about this one. Besides W3-total-cache I also have Akismet and cloudflare and the three of them were working fine with each other before my URL move.
When I look in my FTP I see W3-total-cache-config.php in my wp-content folder and then more W3-total-cache inside my plugin folder as well. Finally I also have a folder in wp-content that is named w3tc. All in all, this plugin seems to live three places in my wp-content folder. Not sure if this is related to my problem or if this is normal behavior for this plugin. If this is an aberration, I can take a screen shot to provide more detail about the locations and folders that W3tc shows up in.

Any help/advice much appreciated, thanks.

ERROR MESSAGE I GET:
Database caching is not available: /nfs/c04/h01/mnt/79775/domains/sandboxla.com/html/wp-content/db.php is not installed. Either the /nfs/c04/h01/mnt/79775/domains/sandboxla.com/html/wp-content directory is not write-able or another caching plugin is installed. This error message will automatically disappear once the change is successfully made.

http://wordpress.org/extend/plugins/w3-total-cache/