This is a common error among D90 owners. The problem stems from the data connection of the lens and body. There is speculation that either the D90 body or kit lens is slightly out of spec causing a poor connection between the lens and body. You can return both the body and lens to Nikon for repair but in most cases its not needed. In most cases the problem disappears after you have swapped lenses several times. To speed up the process take the lens and perform a lock/unlock about a dozen times. The twisting and locking seems to make things right. *Note* My D90 has only experienced this error with the kit lens.
NIKON D90 “CHA” ERROR This error is quite common with Nikon DSLR cameras and shows up quite often with D90 users, myself included. Usually removing and reinstalling the SDHC memory card will clear it up. Additionally if possible format the memory card. I get this error with my two Sandisk and my Eye-Fi Pro X2 SDHC memory cards. This is a Nikon issue. Don’t blame the memory card vendors.