Just purchased ArtRage for the iPad 3 and ran into this bug.
When you select the technical pen (6th from the top) and tap once on the canvas, thereby creating a dot, then grab the eraser, you cannot erase the dot. You have to clear the whole canvas in order to make the dot disappear.
I found this out by accident while the tool picker was open. I thought tapping once on the canvas will close it, so I tapped, but it created a dot and could not erase it. Here are the steps:
1. Open the tool picker.
2. Pick the technical pen (6th from the top).
3. Quickly just tap once on the canvas. Just make a very short, quick tap so it will place a dot on the canvas. DO NOT drag your finger or stylus. Just tap. You can place multiple dots on the canvas by just quickly tapping anywhere.
4. Switch to the eraser and try to erase the dot. You can't! You will have to erase the whole canvas to get rid of it. If, however, you DRAG the technical pen, then you can erase the drawn line just fine.
This bug is ONLY present in the technical pen. I tried all the other tools and they are all ok.