I've been looking for an option to turn on 'eraser accumulation' in Photoshop CS5.5 without success. In earlier versions, the eraser tool could erase an area accumulatively, meaning each time you moved the cursor over a particular area of the image it would erase a certain percentage (based on the opacity setting). In CS5.5 I need to click the mouse every time I want to erase more of the same area instead of simply rolling over it without clicking. I'm praying there is an option that can fix this issue otherwise Photoshop has become useless for subtle editing, or at least extremely tedious. Hopefully someone can point me in the right direction. Thanks.
Please check if you understand the difference between Opacity and Flow (as set in the Options Bar).
I think you're mistaken about what earlier versions did.
Both the current and earlier versions can accumulate erasure if you set the Opacity to 100% but change the Flow to be a small number, e.g., 15%.