there's a problem in calling the url for opening the
popup calendar.
function fw_form_date($input,$name,$trueval="",$error=0)
This is a possible patch:
1. Adding the $CONF variable to the function
GLOBAL $FORM_TEMPLATE,$cur_style,$max_col,$CONF;
2. transform the call to the url in such way
function opencal(name,mon,yea) {
calwin = window.open('" .$CONF[url_base] .
$CONF[dir_framework].
"/popup_calendar.php?mon='+mon+'&yea='+yea+'&fname='+name,'calwin','top=100,left=100,width=300,height=180');
calwin.focus();
}