In lightroom 3 the clone/heal brush isn't working. When I select it to use the cursor does not change from an arrow to the brush and then when I move the cursor over the photograph to take out a blemish the cursor disappears entirely. I have tried restarting lightroom and restarting my computer. Neither of these worked. I searched online and found a ton of other people with the same problem but no one had a solution. PLEASE HELP!! This is really annoying!!!