Gotcha.
In your /modules/Discount_Coupons/discount_coupons.php file...
Change this:
Code:
if ($mode=="add_coupon" && $coupon) {
#
# Check if coupon is valid
#
to this
Code:
if ($mode=="add_coupon" && $coupon) {
$coupon = trim($coupon);
#
# Check if coupon is valid
#