A previous entry had is almost right. There is a small belt that drives the loading and unloading of the disc. If this belt dries out a bit, it gets slippery and will not have enough friction to completely load the disk. This will result in the error you are seeing. DO NOT adjust anything on the laser without test equipment. The alignment of the laser is critical for proper operation and can not be adjusted properly without the correct equipment. You can change the belt however. The belt should cost around $5.