That's our somewhat restrictive security features that notice some object being loaded as part of your webpage, an object that other sites also use. For example, many sites load urchin.js from google-analytics.com. This means that the daily load our system allows itself to subject google-analytics.com to will quickly be reached. Anyone trying to start a new test for a webpage that loads urchin.js will then be denied to run their test.
We have a list of URLS/sites that are exempted from these checks, but this list needs to be populated. So far we only have a few entries on it (like google-analytics). It seems your site loads things from googleapis.com so I added an exception for that address now. Try again and see if it works.
We probably need to work on the information to users whenever a test is denied also. If you know what the offending URL is, you can remove it from your load script and run the test without it.