WPMU DEV Plugins and themes not installing

Using the WPMU DEV dashboard to try and install some of your plugins (or themes) gives the following error..

http://jing.videvent.com/2013-05-26_10-49-23.png

This is a new install of WPMU - I deleted the earlier one (in case you were wondering).

This is a self-hosted site - of course.
Can you please help?

Thanks much.