Hi,
I noticed that in Nuendo 5.5.3. 64 bit on OS X there is an issue with plugin window redraws that wasn’t in the previous 5.5x in 32 bits.
In Fabfilter’s ProQ for example the FFT and buttons will not update until you pull down the analyzer menu, as soon as you let go of the mouse it will not update the plugin window again.
There are other plugs as well with the same problematic behaviour (toneboosters).
Ollie