I'm having similar issues as Skipster (minus the borking, thankfully).
I downloaded the 15sec from XDA to my sdcard. Tried twice, first by "install zip from sdcard" method, followed by a davlik cache wipe--didn't work. Went back, renamed it to update.zip and did it that way, again, followed by a cache wipe. Still getting the darn 3 seconds.
Any ideas?
My SF isn't running anything fancy; aside from root+clockwork and a couple mods, all I've got is Voodoo. No oc's/kernel's yet.