Simply: Text typed with the typewriter tool disappears as soon as the mouse is clicked outside that text area. Enabling the typewriter tool in Reader, then opening the document in Reader, the problem does not occur.

I need to be able to work in Acrobat.

I have spent considerable time seeking a solution, to no avail. A number of posts in various fora, mostly older, address this issue, but the most commonly recommended registry fix has not solved the problem. (The registry fix addresses a mysteriously created color or opacity change in the text in the registry, which is then reset to a value of 1.)

I have updated from Acrobat Pro 9.0 to 9.5.5 with no change in the problem.