download button - how to get file with mechanize

[zak]

hi,

i'm having problems to access the content of a (csv-)file behind a
download-button inside a form:

<form>
....
<input type="submit" class="ButtonDownload ButtonRechts" title="Daten
herunterladen" id="ctl00_cphContent_btnDownload" value="Download"
name="ctl00$cphContent$btnDownload">
....
</form>

any idea how to read or download the file?
form.click_button(form.button_with('ctl00$cphContent
$btnDownload')).body
apparently yields the first line of the file?!