I do not need help on that, and just want to bring something to your attention.
I have a totally separated WP install for testing purpose where I run all kind of beta and RC versions. I installed your WPMU Dashboard today and I guess it's only a CSS issue, it goes below the menu height (all above is empty WPMU blue). This is WP 3.8 Release Candidate (with nightly builds).
I tried going full screen (with a 1900px wide resolution) and it's ok, then back to a smaller window shows issue again. As I know that in WP 3.8 they implemented more responsiveness in the admin, it might be related.
If you want me to test anything specific, I'm glad to help, or even give you temporary admin access in case you cannot reproduce the issue (if it's something in my setup, and if this is relevant, tested on Firefox and Chrome under Windows 7).
I'm not sure when WP 3.8 is due to be released (matter of days I think), in case you want to correct that before.