As you probaly know, this site uses cookies to keep you logged in. If you have 'Keep me logged in' checked this cookie is saved to disk, otherwise it is kept in memory and expires after you close down your browser.
Try this:
If you're using Internet Explorer, select the tools tab on the top (if you can't see it press your 'Alt' button). Select options -> privacy. It should be set to medium. If it's set any higher you'll need to click on the 'Sites' button and add
http://www.harley-davidson-hangout.com to the box, then click on allow.