Hi Arthur,
On the off chance, check to see if the paragraph alignment is set to "Align Top" instead of "Align Middle".
This will set the alignment of the caption and the text that the User inputs.
If you want the caption to be different from the text, you could set the whole TextField to "Align Top" and then using the curser, select the caption text and set this to "Align Middle" if you like.
Hope this helps (i.e. that I have understood your problem ;-)
Niall