Doing a test-site on my local harddrive with Atahualpa v3.4.2 at the moment.

My "ATO-->CSS Inserts" input box shrunk to only 1 row. Similarly, the "Layout Container Style" also shrunk to 1 row. I wish to make modifications but now I can't see the code that I put in previously.

I have reloaded the Atahualpa 3.4.2 wordpress files but it didn't help.

take a look at the right bottom of the box, there should be three angled lines. Put your cursor on these and drag the box bigger.

Found the problem. After I deactivated the "WP-dTree" plugin, my text boxes returned to normal.
But wonder why's that so?

The plugin uses Scriptaculous for display effects and that is probable causing a conflict in the code