I deplore the use of "no problem," especially in a professional setting. My young bank representative says "no problem!" in response to my thanking her for her help. Store clerks say "no problem" when ringing up your purchases. It's mostly a young people thing, I think. I recently told a friend my age that we should offer to teach classes on proper responses. "No problem" would be weeded out, and "yes, ma'am" and "No, sir" and "thank you" would be reinforced.
