2003 Subaru Outback LL Bean
New alternator.  New Battery.  New cables.  (battery was dying in the cold.  We replaced the battery, but it was not recharging.  We replaced the alternator.  Everything seemed fine.)

Driving down the road @ 45mph. 

Feel an awkward hiccup.  Look down.  ABS light is on.  Speedometer and Tachometer are at 0.  Car is still running, and I have not slowed down...
Coming up on a red light...  Hit the brakes, another hiccup.  Airbag light comes on.
Turn on blinker to get off of the road.  Oil temp light comes on.
Pull car into parking lot and turn it off.  It dies completely. (no power to anything)

Disconnect battery.  Reconnect.  Get a jump.  Car comes back on as if nothing happened.

Start driving home.  Make it a few miles...

Hiccup.  Exact same process as before, but I decide to rough it out. (home is ~1 mile away)
I get to a light.  Have to brake again.  Car hiccups again.  No new lights.
Car accelerates but feels like it's dragging...  At 45, Speedometer and Tach come back to life, only to have another hiccup about 5 seconds later, at which point they go to 0 again.

Break and hit blinker to turn onto subdivision road...  The [D]rive letter on the dash starts blinking with the blinker.
Car makes it home without any further symptoms.

Turn car off.  Key is stuck between Acc and start.  (car is in park)
Disconnect battery, reconnect battery.  Key can now be removed.

No blown fuses as far as I can tell.

Short?  Bad alternator?  Bad Battery?  Other?  I'm thinking short, or perhaps malfunctioning computer...  but I figured that I'd ask here before I start tearing things apart.  (or paying the local dealership to start tearing things apart for me)

I'd check and make sure the alt is charging. Make sure the connections are tight. As the battery voltage drops, you tend to start dropping modules. The engine controller usually will run on the lowest voltage of all the computers, but the coil output will drop, which can cause the hiccup.

MANY, MANY reports of either; A. wrong alternator for the H6 being sold by parts stores. and B. Poor quality of parts store alternators.

Thanks for the feedback guys.  Going to try replacing the alternator again.

If you still have the original alternator take it to a rebuilder and just have it rebuilt. Parts store alternators are junk and don't last.

Another parts store alt will probably be the wrong one as well.