If you updated to FW 4.1.0, you'll have to follow the directions in the wiki to jailbreak your device via diags, enable usbnet, then you'll have to restore your screensavers over SSH. (Hopefully the stuff you followed made you do a backup somewhere...).
(FW 4.1.0 broke the data.tar.gz stuff on *main*)
If the failing update you're speaking of *is* the 4.1.0 official update, then, yep, what knc1 said, complain to the right people
. (You don't necessarily need to do a full downgrade, just to restore the default screensavers).
Next time, try to understand the implications of stuff you're blindly following
. [Yes, I'm a bit tired of the whole screensavers mess on the K4, it's not like there wasn't any update/idiot-proof code out there when the K4 was released...]