nevermind, unable to reproduce on both forms....
Could you be suffering from the
single text input fieldproblem?
See http://niwo.mnsys.org/saved/~flavell/www/formquestion.html for a detailed explanation, but I've found numerous weird problems arising from this in my Seam app. Note, you may have more than 1 field on your form, but if only one is a text input form, that will trigger the problems.
I've worked around it by putting a second (dummy) text input on affected forms and then hiding it with CSS.
Or use <s:defaultAction />