Question : Photoshop Eraser Tool Ignoring Pixels

I'm using Photoshop CS3.  When I use the eraser tool it chooses to ignore random groups of pixels.  I've tried adjusting everything in the eraser tool bar but it still ignores pixels.  If i switch to the block eraser it seems to work ok, but the block eraser is lacking, and i don't want to have to clean up after the eraser tool.  Any ideas?

I'm sure the pixels that are "left behind" aren't from an under layer.  I've tested using a single solid color visible layer and it still happens, the eraser tool just doesn't erase it.  

Answer : Photoshop Eraser Tool Ignoring Pixels

I was creating a small example when I found the problem.  I was going to erase several lines using different presets  when I realized I was on the "Dry Media" preset.  The "Pastel rough texture" LOOKS like a normal brush; however, it misses pixels as part of its texture.  Thanks for the reply and sorry for false alarm.