Advanta Corp., facing a first-quarter loss for bad credit card loans, said that it may put itself up for sale. The company, based in Spring House, Pa., also said Chief Operating Officer David A. Brooks resigned after two months on the job. Investors were taken by surprise as Advanta said it would report a loss of $20 million, or 44 cents a share. Shares of the ninth-largest credit card issuer fell $8.50 to close at $31.875 in Nasdaq trading. "We expected some loan losses, but everyone is surprised at the extent of the problem," said Mark Girolamo, a Bear, Stearns & Co. analyst.