Nikon has issued a service advisory for CL-L2 case users (that includes all 200-400mm lens users, as that case came with that lens). Basically, the bottom of the case may crack and eventually allow the contents of the case--your precious lens--to fall to through.
Unfortunately, Nikon uses the word "affected" over and over again in the service advisory, which makes it unclear to some whether you have to wait until you see signs of a crack before returning the case for replacement or not. Apparently, the use of the word "affected" is meant to separate out cases that don't have the letter T on the bottom from the ones that do. A T on the bottom of your case means you have a case that meets Nikon's standards. No T on the bottom of your case means that you should apply for a free replacement. US customers can apply for the CL-L2 replacement here or call the usual Customer Service number (800-645-6687). Nikon will pay the shipping costs both for the return of your potentially problematic case and your replacement one.
In the meantime, if you're using the CL-L2 soft case to carry your 200-400mm, 400mm, 500mm, or 600mm lens, you should inspect the integrity of the bottom immediately. If the very bottom has a T stamped on it, you're fine and should just continue using your current case. If it doesn't have a T on it, don't continue using the case unless you've verified that there are no problems with the bottom.