I just can't get WU to work, always getting same error code - 8024400A. Tryed ro fix it i several ways, hours of googling about but still nothing. What's wrong with it?

Had the same problem and post a error report, problem went away with 5744

Vista 5728 NOT recommended to be evaluated, it's already replaced with 5744 or roll back to 5600

FYI different people work on different betas so I might have an unreleased version that might have a problem and its ok to bring this issues to this forum. However current builds have fixed the issue

upgrade to build 5744