I had a search on the web and some testing yesterday...
Strange enough... I found a similar problem which was related to switching off Vista Aero (theme)...
In Vista (and other windows versions) it's possible to switch of the theme service. Windows Vista then basicly runs in "classic/gray" windows mode (no glossy/glassy effects).
Most fanatic gamers, producers, powerusers etc. turn these services off while it is likely to win some cycles of the processor power that way. (I guess this would be marginal.. but hey...)
However... Don't ask me why... Some people experience more lag when turning this service off.
I tried it yesterday with theme services on/Aero theme as default theme.. and the "tearing" was gone for 90%... However.. the output still seems a bit shocky/not fluid. (On the projector output, but also on the preview insinde Avenue!).
While the problem is visible on the projector and also in the preview, I can't imagine it being a refresh rate problem. Otherwise everybody should experince this problem. (I think most users using their projector and laptop screen @ 60 Hz and never changed it or even had a look at it

).
I also played a lot with the global and program specific NVidia settings, but I don't see any difference in performance (I changed almost all parameters to all possible settings to try)
The specs of my laptop are in my sig.
Anyway.. I'm curious if other (Vista) users benefit from turning on Aero theme and windows theme service...
Thx for looking into it!
PS. I did some more testing, using Winamp's visualisation Milkdrop 2.
I did not change anything to graphic settings. (compared with Avenue)
The output is flawless, no hickups/tearing.
Probably I can't compare this output with Avenue's output, but it seems to me that if the refresh rate of the output was wrong, it would be tearing on most applications with video or fast moving images.
The other way around... Avenue is the only application sending more frames than my refresh rate and all other applications are just slow or just in time ?!?