Barclays once blocked all of my company accounts for a week but never told me. Eventually I found out when stuff bounced. When I rang up to find out why they (no joking) asked me to explain why I had transactions from something called "Federal Reserve" (it was part of a US government contract).

I explained why. Then they asked me to explain who this "Federal Reserve" was. I laughed thinking they were joking...Then found myself having to actually explain it. They then had me on hold for ten minutes when they checked with their manager...