[getafix]

I have been experiencing stuttering while watching HD movies streaming from a NAS over gigabit network. I discovered that if I ctrl+alt+del to task manager and back to XBMC, stuttering is completely gone. Smooth playback. I know that this is not a solution, but maybe someone more wiser could shed some light on why it happens.

I have tested it with Avatar, 2012 and Dark Knight - all HD MKV's and all do the same thing.

[Voyager]

Have you already tried to disable Aero? (With Vista/7 on your XBMC shortcut properties, check "Disable Desktop Composition").

Aero is known to cause stuttering if you have "auto refresh rate" turned on in XBMC.

What you describe as a "fix" was already suggested as a "hack" (actually simulating an Alt-Tab keypress and back) but turning off Aero is more effective. In that case, just make sure that you also set XBMC to use true full screen, otherwise you'll have "tearing."