admin->accounts->new user broken under marvin theme

Using current CVS core and themes, I am unable to get a page to display when navigating through the menu to admin->accounts->new users. Sometimes the browser just hangs until it times out, other times I get an empty/blank page pop-up warning from the browser.

Strangely, the web server logs variously says 0 bytes were sent, or 6720 bytes were sent.

This same menu navigation works fine with the chameleon theme.