I am not sure how many people downloaded, looked at, or are actively using that SurveillanceSaver alpha 0 that made the rounds a few weeks ago. It seems that enough people are using it that the cameras are overloaded (slashdotted, dugg-effected, whathaveyou) and can only intermittently serve up images.
The way the screensaver is coded, it requests an image every second, then displays the results of that to the screen. If the request was not fulfilled (from the camera being flooded with others’ requests and unable to process yours), it would display a black screen for that second. This would result in choppy video–with the image cutting out for a second every few seconds.
I made a minor modification to the screensaver that effectively caches the last known-good image. With this enhancement, the picture you are looking at may be a little stale, if there were several bad requests in a row, but you should never get a black screen (unless, of course, the camera you are looking through is in the dark.)