Okay, I think I know what the problem is here. It's different from anything that's been mentioned so far, so please read the following calmly and don't expect it to be a rehash.
(Note to people who are suspecting Aaron of using CSet 6: that is probably NOT the problem, so stop accusing him, please.)
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Aaron, here's a brief explanation:
You know how sometimes the translucency gets totally fuggered up in ZQuest when you switch between maps? This is because to display translucencies, ZC/ZQuest has to "check" to see what colors it has available. If the available colors change (i.e. from giving Link a ring), translucencies will immediately be screwed up until ZC/ZQuest "checks" again.
Here's the problem: in ZQuest we can tell the program to "check the colors" at any time by pressing "B." In the ZC player, there is no way to manually tell it to do this, because it's supposed to do it automatically. Sadly, ZC is imperfect, so we have to work around its various problems.
You are using a cheat to give Link a blue ring. The problem there is that CSet 6 switches to the blue ring CSet IMMEDIATELY, and that leaves ZC confused about the colors that are available. Cheats aren't the only way to cause this problem, though, because ring CSets are an "Old Feature" while translucencies are a "New Feature," and sometimes New and Old don't play well together.
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Here's the easiest way I can dream up to fix the problem:
1. Have Link pick up the ring item on a screen that doesn't use any translucencies.
2. Make sure Link can't access any other screens that use translucencies UNTIL he warps to a new DMap.
3. To be doubly sure that the palette is rebuilt, make sure the new DMap uses a different palette than the first DMap.
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The above method SHOULD work. However, be warned: many versions of ZC/ZQuest are buggy. I've encountered instances where translucencies just do not work no matter what I do, particularly with enemy shadows. Ideally, you will be able to avoid this with your tree shadows, but expect ZC to be imperfect.
In some other cases, pressing the "B" key in ZQuest does not fix the translucencies. If this is the case, you can fix it by saving and restarting ZQuest. Unfortunately, that's the only way to override that bug once it starts occurring during a ZQuest session, but at least it works.
If anybody has any questions, please ask them before getting upset, contradicting me, or accusing anybody of doing something stupid. Thanks.