MGB Runs/Does Not Run

["Mike Razor" <mrazor@mis.net>]

 Warm up engine for a couple of minutes only, rough idle.  Take on off
and get to the top of the hill, about 1/4 mile away and the car stops
dead in its tracks.  No warning, just quits.  Try several times to
start it and it won't start, push it to the side of the road, it
starts and runs for a couple of seconds then dies, cuss the car, try
and start again starts and dies, cuss some more, try one more time it
catches and runs just fine.  Drive it around does OK, but kind of
ragged.
Help!
MIKE R