Ok I think I found the issue. It happens only when you have shipping, on joomla 2.5 and with the CSS display mode configured for the buttons.
Change the code:
if(shippings) {
shippings = shippings.value.split(";");
for(var i = 0; i < shippings.length; i++) {
if(!varform.elements["hikashop_shipping_" + shippings[i] ] || !isSelected(varform.elements["hikashop_shipping_" + shippings[i] ])) {
alert("'. JText::_('SELECT_SHIPPING',true).'");
return false;
}
}
}
to
if(shippings) {
var selectedShippings = new Array();
if(shippings.value){
selectedShippings.push(shippings.value.split(";"));
}else{
for(var a=0; a < shippings.length; a++){
if(shippings[a].checked && shippings[a].value.length>0) selectedShippings.push(shippings[a].value);
}
}
for(var i = 0; i < selectedShippings.length; i++) {
if(!varform.elements["hikashop_shipping_" + selectedShippings[i] ] || !isSelected(varform.elements["hikashop_shipping_" + selectedShippings[i] ])) {
alert("'. JText::_('SELECT_SHIPPING',true).'");
return false;
}
}
}
in components/com_hikashop/views/checkout/view.html.php and that should fix the problem.