[nttdemented]

Ok just to be totally sure, remove EVERYTHING from the exception list in FlipIT and leave all angles enabled globally with the sensor check mark. Ok out of the program and soft reset and see if your phone does indeed flip. You can also try calibrating your gsensor with the sensor calibration utility in your settings control panel. If it doesn't work after that there might be something configured in your ROM that isn't allowing FlipIT to access the gsensor. Does Opera flip to landscape like its supposed to? (It does so without having an app like FlipIT installed).

Once you get the app working the exclusion list is used by adding either the name of the executable that runs the app (for example, manila.exe or tmail.exe) you want to rotate or the name of the window it opens (class name) (the name as it appears on the title bar).