1. Start Levels and Color Tool, go to the Amount control and click New mask...
2. Create a mask
3. Go to the transformation window and edit either of the controls: Midtones, Contrast, Color Balance... -> no change to the output image
4. Click on the output image - the cursor changes to a small cross -> PWP closes.
To bring PWP to a unwanted close down the steps 2-3 are not necessary. After the mask window opens, click on the Levels and Color Tool title bar to make it active and then on the output image.
Also, while working with the tool trying to combine both masking tools I also encountered a considerable slow down of PWP on the brink of freezing.
Levels and color tool - conflict of masks
Moderator: jsachs