I created a simple gadget on a dashboard meant to be shared to all users. It is 'Running Builds' gadget, which takes a single parameter, Configuration Path, which I set to a configuration which usually has 3-4 builds running concurrently.
Periodically and for random periods of time, this gadget shows no builds running. I haven't had the patience to pay close attention, but it might happen whenever a build finishes. The text in the box is 'No running builds for specified configuration'. However, looking at the build configuration overview shows the running builds (as well as all finished builds). I can post screen shots if it will help.