i had a similar problem.
i changed the following:
file: administrator/components/com_virtuemart/classes/ps_cart.php
lines 120-124
before:
if (!ereg("^[0-9]*$", $quantity)) {
$vmLogger->warning( $VM_LANG->_PHPSHOP_CART_ERROR_NO_VALID_QUANTITY );
return False;
}
after:
$quantity = ereg_replace(",",".",$quantity);
if (!ereg("^[0-9]|[,]|[.]*$", $quantity)) {
$vmLogger->warning( $VM_LANG->_PHPSHOP_CART_ERROR_NO_VALID_QUANTITY );
return False;
}
this code is for adding the product to the cart; as we need this also when updating the cart, I changed the corresponding lines around line 278-282.
as for the database, I changed in table: vm_order_item the field
product_quantity to double(11,2).
I have not tested it thoroughly, but it seems to work properly.
the ereg_replace containing "," is need for me, as my shop is located in germany and the comma is used for decimals. if you are working with "." as decimal separator it is not needed.
I have no idea if this hack produces bugs elsewhere in the system, but I don't see that there should be a problem.
plz have us your feedback if you try this hack...