I just tried to get the Update for Poser Pro 2012 from my office pc (no installation of poser here...). I get the same message as you, but I get also a popup where I can type my serial number in (the error message is dark in the background underneath). Would I type my serial number, I would be able to go on for the update (have done that before already, so I don't go further at this point of the test...).

If you don't see the popup that asks for your serial number, do you perhaps have a popup blocker active?