Hmm...
I had an 820 from my LFS that was like that, for about 2 days. It was like a bad comedy skit. I'd slap it around, it'd run. I'd turn my back it'd stall. And, like my shampoo bottle, I'd lather, rinse, and repeat.
About the 6th time this happened, I invented a few new words, took it back, sucked up, and called Marine Depot for a Stream. Incidentally, I also didn't eat for a week.
I just got paranoid it'd stall, etc, while I wasn't home, no circulation, mass die-off, locusts, you get the idea.
They're good pumps, but if I were you, I'd exchange it for another 1100; you either seem to get a good one, or not so good. Take it as an omen, exchange if for a different model. Any reputable drygoods store should swap it out if you explain...
-Andy/Oldimpala