A brand new serpentine belt shreded off a piece ~1/8" within 12 miles Why?

What is your question?

Installed a brand new Serp belt and took it for a 12 mile test drive. Upon return the belt had shredded in the exact same position as the old belt approx 1/8" strip around the entire belt. What causes this problem? Could it be a bearing in one one of the components (alt, water pump, A/C) or could it be a problem with one of the pulley wheels? The top pulley wheel has some (slight)wear grooving but nothing significant.