Which Barclay's card did you have?
I use my Travelocity card in a similar way every month. I usually rack up a balance of about 85% of max, then pay it off in one lump sum.
EDIT: Also, how many points did you have accumulated? Maybe that had something to do with it? I've been cashing in about $3k of rewards per year -- far, far above my $79 annual fee. I've been wondering for a while how they could possibly be making money off me?