FYI, on this machine I'm running two monitors - anyway, for some strange reason, now YoWindow (on my main monitor) shows as a tiny window in the left, upper part of the screen and on monitor two the second screensaver (bubbles) shows ok but with YoWindow too, also as a tiny window in the left, upper part of the screen at the same time!
I have looked into this further, and have some bad news. It appears that the YoWindow screen saver is poorly constructed, and doesn't follow the screen saver conventions from Microsoft. For some reason this screen saver has a hard-coded preview size, which is why it is appearing as a small box. This is unfortunate and requires the screen saver to be fixed, not DisplayFusion, sorry.
