WPMU Dev Updates succeed, but Installs fail with "Install package not available" error.

It seems I can no longer install new WPMU Dev plugins on my website. I have ruled out as much as I can think of. I’ve searched for errors in the apache errors_log, but can’t find any. I’ve validated that I can connect to premium.wpmudev.org from my web server. In fact, the automatic updates from the WPMU Dev dashboard are successful. It’s just the new installs that don’t work.

I’ve also already tried replacing my API key, as mentioned on previous support calls, but once the new API key made its way through the system and the INSTALL buttons re-appeared in the dashboard, clicking the INSTALL buttons still gives me the “Install package not available” error.

I’m specifically trying to install the Google Maps plugin, the Google Analytics+ plugin, and the Multi-Domain Support plugin. All three of them fail.

I can’t find any hint of the problem in any log. Please let me know how I can enable more detailed logging or some other way to find out why these install attempts are failing.