Bad Alternator? or what?

Listening to radio for an hour or so, try to start car, nothing. Battery reads good, jump it anyway, no crank at all. Replace starter, cranks and starts instantly. Drive around the block, car stalls, try to start, no crank. This time I jump it, and it starts right up.

Battery terminals read 14.8 V at idle. Alternator tabs read (big one) 14.8 V, (small one on top) ~8V, (small one on side) less than 1 V. Alternator gague in dash is in middle, moves slightly to the right when I turn on the lights, or anything electrical. Voltage reg and alternator are a year old, voltage regulator has good ground.

WADDAYA THINK? thanks guys.