Check in the player's Options menu to see that the pathway to the sample location is correct. This problem usually arises when users override the default C Drive location for the samples at the time of installation. We strongly recommend that users let the program install the samples on the C drive to avoid this issue. Since all samples are intended to be loaded in RAM no performance advantage is gained by placing the samples on another drive. Anyway, if the samples are placed on a drive other than the C Drive then the pathway in the Options menu must be correct for the samples to be located.
I would suggest reinstalling JABB. Make sure you let it install on the C drive and see if that solves the problem. If not, you may need to contact Native Instruments tech support to see what the problem might be.