I don't personally have much experience with cats, but have heard that they are ultra-sensitive to household smells that we humans cannot detect: colognes, air fresheners, cleaners, etc.
As someone else suggested, maybe the kitty doesn't like that brand of litter-or there is something (noises, foot traffic?) upsetting them within the litter box location, etc.
1990 Univega Alpina/(stock) gel saddle
2009 Specialized Dolce Elite/BG Lithia saddle
2009 Jamis Coda Sport/Selle Royale Respiro saddle
2010 Jamis Aurora/Jamis Touring Sport saddle