This seems to happen quite often, it's baffling.
In 1992, I bought a flat. I applied for a mortgage with Halifax, and was turned down. Slightly gobsmacked by this, I asked them to explain why.

They didn't say much, only that I had some issues with credit, which was news to me.

Several weeks of checking later, via some dodgy rating agency, and in fact a bit of help from my bank manager, a piece of paper turned up stating that I had an unsettled outstanding with Visa, which was considered a default.

Another week or so playing phone tag with Visa reveals that my account had an outstanding balance of £0.00 on it, which for some reason their computer had decided was a debt.

Fotunately a human was able to tell their system to bugger off. A bit more work with the credit agaencies and the Halifax, and I got the mortgage.

Awful lot of work for a non existent debt that I had no idea about though.
(username failed moderation, Thu 1 Mar 2012, 8:35, Reply)