Did someone else experience slow fading in Qt applications, for example when opening a new dialog from a main window? I'm running Ubuntu 12.04. LTS and Qt 4.8.1.
The application where I noticed that does some opengl rendering in a qglwidget. When the application runs, also other windows not belonging to the qt app are affected by slow fading in/out. The thing is that the qt app only uses 20% CPU load (also compiz) so I assume it's not caused by a high CPU load...
Are yours videocard drivers up to date?I had the same problem (using opengl through QGLWidget) and updating solved the problem.
If this isn't the solution,paste us some code.
Hope it helps.