Not trying to "dog pile" on this thread, but Adobe aggressively priced the Elements 10 product lines on Black Friday (that's when I bought it) and I would imagine a LOT of people purchased too. So, I believe their support team will be swamped with frustrated customers. I would expect that with this newly-found issue that there should be a warning on Adobe's support Web page as early as today.
I just looked: http://www.adobe.com/support/premiereelements/. Nothing at all. Also, the list of most active support items is with Premiere Elements 7 which is how old?
I've had issues before with Adobe software on Windows (msi temporary folders can't be written to) or where deactivation and concurrent installation limits cause issues, but I never would have thought a date would be the culprit.
I have it installed now. Thank goodness.
On behalf of Adobe, I'm really sorry about this. For anyone else encountering this issue, here is a summary of solutions, direct from the product development team:
Cannot install Premiere Elements 10 on Mac OS
If this does not solve the problem, please do post and let us know.