Steps to reproduce:

1. Go to Manage Jenkins --> Configure System
2. Under Cloud section, click "Add a new cloud" and select "VirtualBox".

Actual behavior:
Nothing happens.

Expected behavior:
VirtualBox cloud configuration should be presented.

Debugging with FireBug I see the following request comes back as a 404:
http://myjenkinshost/$stapler/bound/a3961942-2fe9-4571-856e-42a7fa313fea/render?%5B%5D=

Header information:
Response Headers
Server Winstone Servlet Engine v0.9.10
Content-Length 263
Connection Keep-Alive
Content-Type text/html;charset=UTF-8
Date Mon, 21 Mar 2011 22:11:11 GMT
X-Powered-By Servlet/2.5 (Winstone/0.9.10)

Request Headers
Host myjenkinshost
User-Agent Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110303 Ubuntu/10.10 (maverick) Firefox/3.6.15
Accept text/javascript, text/html, application/xml, text/xml, /
Accept-Language en-US,en;q=0.7,en;q=0.3
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 115
Connection keep-alive
X-Requested-With XMLHttpRequest
X-Prototype-Version 1.5.1.1
Content-Type application/x-stapler-method-invocation;charset=UTF-8
Crumb 282e03e6-3f8a-4386-8853-439a80a15a21
Referer http://myjenkinshost/jenkins/configure
Content-Length 2
Cookie screenResolution=1600x1200; Apache=<ip>; country=US; firstname=Mike; uid=mrobinet; pcn=341