firstly, theres no real need to use screensavers anymore, unless it's there purely to please the eye?
screen savers do use up a lot of system resources, if your running other programs in the back ground, this may effect it
a way of testing to see if its just draining all your resources: press ctrl+alt+del, to bring up task manager, click on the performance tab, you will get a line graph detailing CPU usage
put your screen saver on (with task manager still open) for a few deconds, and then turn it off. now look at the line graph, does it run high, into 90-100% CPU usage? if so, its purely because its sapping all your system resources.
try that, and lets us know what happens