IDE won't start in Win 8.1

Noob, here. No splash screen, no process running in task manager, nothing. Tried 1.0.6 and 1.5.8 (That's a mighty big version spread, but that's what's on the website!) Got the USB driver installed just fine (shows up as "Arduino Uno (COM3)", just can't run the IDE--even as administrator. What might I be doing wrong? BTW, I tried the EXE version installer and it did the same thing, so I downloaded both ZIP files and tried them. :confused: