I've installed PD9 yesterday and it seems a lot more stable than PD8 and has more HD options for input and output that I was looking for. So I gave it a swirl and as exercise tried to add titles to an existing 720p movie. Initially that worked fine and the titles showed in the title window as well as previewing the entire movie.
But after a few titles suddenly the titles did not show anymore in the preview window when playing the movie.
I noticed the eye/cross icon at the left side of the title track had gone (or was never there to start with - I did not paid attention to it at the start).

Other people have also run into this problem and it is indeed solved if the title blocks are moved to another movie track. But that is obviously not the intention. Also, it doesn't allow to make a production with or without those titles (the function of the eye/cross icon).

I've removed/reinstalled PD9 but that seems to make no difference. The eye/cross icon remains absent.
Opening the original project with the invisible titles showed them still invisible. And new ones added were also invisible.
Removing the movie and replacing it by the one that came with installation (nature.mpg) made no difference. Titles not shown.

However, the odd thing is that starting an entirely new movie and using nature.mpg again, I could add titles in the title track and they do show - but the eye/cross still missing. The only way now not to show them is physically remove them entirely. Re-importing the 720p movie I started with initially, also showed the titles while the eye/cross is missing.

I'm puzzled to say the least. The screen capture enclosed is of the new project (where the titles show) but the eye icon still missing.