I have tried several custom themes and some of my own creation. I see an issue less on themes that are not really that much different from the stock themes. The issue is, that sometimes if you move your trackball too fast, the selector indicator disappears. I end up having to move the track ball around again in order for it to come back up. I hope this makes sense. I don't think this is just an issue I am having, since this happens on my 8900 and use to happen on my 8300. I usually end up going back to the stock Zen theme since there are no issues with it.

Hope someone can shed some light on this for me.

I've only typically seen this happen on the application screen, and this is due to the theme builder. Plazmic released this last one with a lot of little issues, a lot of people think that the latest theme builder shouldn't be the official but they don't seem to be releasing a new version any time soon.

It's not the theme developers fault, it seems to be the theme builder program itself