Here are a few questions that will help us find, duplicate, and hopefully resolve the problem:
What exactly did you do before / after the problem happened? What price did you put in? What is different from other times you've posted in the BSA section?
How long has it been happening?
Which browser and version are you using (eg., Firefox 3.5.9, Internet Explorer 7, etc.)
Have you logged out, deleted your internet cookies, logged back in, and tried again?
Have you tried a different browser?
Have you tried a different computer?