I notice this 3 second stutter (as I call it) in TOH (steam version) in the challenge-missions.
I decided to completely re-install TOH last week and that cured it for a while, but today it's back (after the automatic update, for that matter).
It's a stutter in the graphical presentation every 3 seconds for maybe half a second. Very annoying.
I run the steam version of TOH on Windows 7 Home Premium 64-bit; Intel Core i7 @ 4 GHz with 8 GB RAM.
greets
Digger57