Sparrowlight, thanks for your help. And thanks for the help of ixtab and geekmaster, et al, on the other thread that you pointed me to. All is good for me now.
I uninstalled the simple screensaver hack, then uninstalled the old custom screensaver hack, then uninstalled the jailbreak. Reinstalled the jailbreak and the simple screensaver hack, but still no screensavers. I then copied my existing "screensaver" folder to my C: drive to save my images, deleted the screensaver folder from my KT USB root drive, uninstalled and reinstalled the simple hack. I had screensavers back and can now put my custom images back in my screensavers folder in the USB root drive. (I also think I named them wrong by including the .png extension in the image names.)
So, I finally did figure it out, and thanks to all here for their help, the jailbreak, and the hacks.
(Forgive me if this counts as a cross-post, since I did put a short update on the KT jailbreak thread. I just wanted to update and thank Sparrowlight for providing the link to the other thread.)