When I use the brush or eraser, a Ø symbol pops up next to my cursor and prevents me from drawing a stroke. Does anyone know a solution to this issue?

Question

Whenever I use the brush or eraser tool, during every other stroke, I get a Ø (circle with a line through it) sign next to the brush shape/cursor and can't draw. Please help, it's extremely frustrating and disrupting my workflow! I am drawing every animation frame so you can imagine, every other stroke is quite often.
There are locked layers below my active drawing layer, which makes me wonder if Flash is just trying to tell me I can't draw on those layers, but I know that   Plus I need those layers there to guide my active layer's drawing. I've never run into this issue before with layers being locked and such. What am I missing?
Any insight is appreciated.
Thank you!

Answer 1

Hmm interesting theory...I do press undo a lot, but only because I'm trying to get a good-looking brushstroke down, usually I don't even actively lock a layer as a step during my session because they've already been locked previously and I don't need to lock/unlock them often. The thing that is frustrating is that I will try to make a stroke, and can't because the symbol pops up...then I'll make the exact same intended stroke again and then it will work fine. It's pretty haphazard but basically every other stroke or every few strokes, it'll pop up.
I think I'm beginning to almost accept this rhythm in my workflow
I'm using CS6, and I noticed that I don't have this problem when I bring the file to work on at my job (CS5) or at school (CC).
Edit: I tried to test your theory by drawing as much as I could without pressing undo...I was pleasantly surprised to not run into any issues with the paintbrush, but sure enough, as soon as I switched from the paint brush to the eraser, and tried to erase something I just drew, the eraser popped up with the "prohibited" symbol.