Finding source of sibilance


I've recently put together a few new components. A Clearaudio Concept TT, the Clearaudio MM cartridge, and the Pro-Ject Tube Box DS. Together, I'm not loving the result. The highs sound actively bad and sibilant. Is it possible that I installed the cartridge incorrectly, or is this just not a good setup? I would assume the TT and cartridge themselves are meant to be together. Any help would be amazing!
128x128andbaron
First question, as slaw is saying, does your system have sibilance problems when using sources other than the turntable?  If so, more information is needed.  If not, you might check the alignment
or VTA of your cartridge, that could be a cause of the problem--in my setup, for example, if the cartridge is set up so that it is not parallel to the platter and it is instead leaning forward (i.e., the back is higher than the front, looking from the side), the highs are accentuated. 
Sibilance can be caused by even a small degree of cartridge misalignment. But it can also be caused by the stylus being attached to the cantilever slightly "off" by it's maker, or even the cartridge being run with too little tracking force. A qualified turntable setup man in your area is a blessing! If you provide your location, perhaps someone can recommend one.