Whenever I use the slow time shout (or any thing that uses the slow time effect) I get half the duration. This is with no mods active. I have tried uninstalling and reinstalling skyrim and deleting the skyrim folder in steam and in /documents/my games/

I've tried starting a new game (multiple times) and using all different shout levels. Each time I get the same effect: half the duration (and I suspect half the magnitude, things aren't very slow).