You probably need to enable cookies. That's how Content Paradise handles everything. That seems to be the common issue around the boards.

Also, you must be registered, including using the link they send you when you register. That could be your problem as well.

As for using Content Paradise within Poser, I don't blame you. It is definitely buggy, and really serves no purpose other than bloat. It is simple enough to go via normal browsing.

All in all, the update shouldn't even be on CP. It should, at the very least, be located on the "update" section of the Curious Labs site, if not built directly into the application to begin with!

You probably don't need the update, since as you have most likely seen above, it doesn't fix anything. I would just try again since CL will probably use the same method to give out the "real update" at some point, and you probably want to know it works for you in advance.

Good Luck.