In a large bowl mix together the Dijon mustard, sour cream, garlic, horseradish, honey, seasoned salt, pepper and chili flakes; remove about 3/4 cup and chill the remaining mustard mixture for 5 hours.
In a large glass bowl toss the chicken cubes with the 3/4 cup mixture; cover and chill for 5 hours.
Remove the chicken and discard the marinade.
Thread the chicken on skewers alternating with the red bell pepper.
Grill covered over medium heat (350-400°F) for about 12 minutes or until done.