We have received a few sporadic reports of iScreensaver Personal 4.4.2 crashing. Because we are not able to contact our customers who purchased through the Mac App Store (MAS), we have no way of getting information from you to follow up. If you are a MAS customer, please create an account on the forums and post your issue here so we can provide technical support.
Please note that if your screensaver contains video files, and it works in Test mode but not as an actual screensaver, the problem is probably just the video codec issue.