A Texas-based firm that makes privately minted medallions claims that Capital One shut down its merchant account after it began making commemorative bitcoin coins.
Mulligan Mint introduced its bitcoin coin last month to celebrate the crypto-currency's success and "principle", says a blog post from the libertarian-inclined company.
The silver and copper coins feature the bitcoin symbol on the front and a QR code on the back that when scanned with a smartphone takes the user to Mulligan's site.
Capital One is accused of panicking at the sight of the word bitcoin and mistakenly assuming that Mulligan was accepting the currency, in breach of its policy.
Mulligan says it has contacted the bank to explain the "misunderstanding" and that customers can still pay via PayPal. The bitcoin coins are still on sale.
The "reaction illustrates just how large an impact Bitcoin and other complementary currencies have had upon the financial establishment. Just mention the name and chaos ensues," says Mulligan's blog post.