slow mixer in N5.5

I noticed that the mixer graphic has become incredibly slow with N5.5. Very slow changing views, slow meters, especially the wave meter. When I press F3 it takes almost a sec for the mixer to appear on the screen.
No problems in 5.1.
Anybody else experiencing this?
I am on Vista32. Aero on or off doesn’t make any difference.
Does anybody know how to improve graphic response?