I have one layer set to Mask and another to Masked. When I add a new layer, it automatically becomes Masked. However, if I change the new layer to Normal, it causes my old Masked layer to become Normal, too. What gives?
Masking involves two layers: one Mask and one Masked. They must be directly adjacent, with the Mask layer on top of the Masked layer. If the new layer you added is between the two, changing it to Normal will require the old Masked layer to be Normal, too. You have to get that new layer out of the shadow of the mask before you change it to Normal. Often you can't even drag the layer down (it just stays in the shadow of the Mask layer unless you drag down and to the left). You should be able to drag it up above the Mask layer, and it will change to Normal; then you'll likely be able to move it back down (below the Masked layer) with success. However you must maneuver it, just realize that both the Mask/Masked and Motion Guide/Guided features require at least two adjacent layers.
I created an elaborate Motion Guide and have the guided layer successfully following that guide. But why doesn't my animation look good?
A Motion Guide certainly doesn't ensure a good looking animation. In fact, in many ways it can become a crutch. I actually recommend avoiding Motion Guides except when approprite. If you step back and really think about the visual message you're trying to communicate you might find just a few carefully placed keyframes will make a more compelling animation.
I used three instances of the same symbol in my Mask layer but only the first one I placed is behaving like a mask, the other two are being ignored. Why?
I can't say exactly why but I do know that you need to break apart symbol instances (or Drawing Object shapes) when you have more than one in your Mask layer.
I made a Guide layer and then I made a 40-frame motion tween. I was careful to set the layer's properties so there's a Motion Guide layer above my Guided layer. However, when I try to attach the contents of Frame 40 in the Guided layer to the Guide layer, the Guide layer is missing. Why?
It is likely that the duration of the Guide layer is less than 40 frames (it's probably just 1 frame). All you need to do is extend that layer by selecting Insert, Timeline Frame or pressing F5. Don't use Insert, Timeline Keyframe (or press F6) because that would be necessary only if something is changing visually in that layer and you probably just want the Guide layer to remain static.