The following xscreensaver modules assume that the default background color is black: spotlight wander shadebobs ccurve interference bumps If *background in .Xresources is set to something other than black, these modules will use that color. With some modules, this results in the screen flashing to the background color before then switching to black; with other modules, the background color is used throughout the module's operation, resulting in some strange effects (spotlight and shadebobs are good examples). The problem can be fixed by adding "-bg black" to each module's command line in xscreensaver-demo, but the more proper way to fix this would be to fix each module...
This doesn't appear to be the case for any of those, in xscreensaver 4.05. If it's still happening for you, please show me the contents of "xrdb -q" so I can reproduce it.
No, can't replicate it under 4.05, so it's probably best for everyone to just close this one out...