I also had the same problem. I also had tried what you had tried. Then I change my method not to use jquery but by using "onsubmit" attribute in the form tag.
<form onsubmit="thefunction(); return false;"> It works.
But, when I tried to put the false return value only in "thefunction()", it doesn't prevent the submitting process, so I must put "return false;" in onsubmit attribute. So, I conclude that my form application cannot get the return value from Javascript function. I don't have any idea about it.