I had mentioned this before in a previous post, but it sounds like you're not keeping your cookies. Make sure your browser doesn't automatically delete cookies from GOG.com. A cookie is involved in redirecting you to the front page, otherwise you'll get bumped back to the teaser pages. While putting your access key in again at the GOG.com/beta site will let you in again, your access key is only valid for a finite number of activations. If your access key expires and you no longer have your cookie, then you'll probably have to contact the support staff and try to get them to activate your access key again. Sadly, this happened to me when I started using GOG.com shortly after it went live; can't say it was my finest hour.