short freeze every 4-5 seconds in web build

Whenever I build a web build (so far only 2 games), my games always seem to stutter a bit. It freezes for a fraction of a second every 4-5 seconds. I don't have this when testing in the editor. these games barely use any CPU and memory, so it can't be that, plus I got a really good pc. And it doesn't seem to be correlated to any specif action, just every 4-5 seconds.

Any idea what could cause this ?

Kinda vague, I know, but any thought on what could cause such behaviour could be useful

EDIT:

I use Unity 3.1.0f4, but both projects are projects originally started in version 2.6. You can play the first here. But it's strange, I don't have the problem anymore at the moment. Yesterday it was all the time, and mostly in my other game (which I can't show because I haven't uploaded it anywhere yet)

EDIT2:

I've got this again, but it seems I've got it in every unity web game, so I guess it has nothing to do with my games. Seems like a problem with the web player (or the browser, or my pc, or windows, or Aero (as mentioned below), or...)

You should also check the version of the web player.

Deactivating Aero on Win7 could help (causes sometimes issues when updating 3D content). Maybe you can try that also.