Version: 2.70 official (win 64)
How to reproduce:
- Paint a nice picture in the image editor of the provided .blend.
- Be sure to spend a lot of time on it and paint something you're really proud of.
- Perform an action in the adjacent 3D view or any other window and undo it (ctrl + Z)
- Notice that your beautiful painting is gone.
"Undo" should only undo the thing the user just did, not the thing the user just did AND all the painting the user did as well.