LONDON (AP) - A Y2K-triggered failure in credit card swipe machines caused frustrating delays for thousands of retailers and customers trying to ring up purchases across Britain Wednesday. The machines, manufactured by Racal Electronics and supplied by HSBC, one of Britain's largest four banks, improperly rejected credit cards because of a failure to recognize the year 2000, a bank spokeswoman said. The Y2K glitch appeared to be the most serious to come to light in the days leading up to the new century. Retailers claimed they have so far lost $5 million in sales due to the problem, and are reportedly threatening to bring a class action lawsuit against the bank. Linda Stryker, a public relations executive for HSBC in the U.S., said the error should not hit any U.S. credit card swiping machines. She said it was specific to software used in machines in Britain.