Just following this up as I have run into the same issue
I have exactly the same issue after running the eCart checkout wizard, the relevant block of code looks like this:
if (WA_eCart_UPS_IsTrueValue("true")) {
$Shipping_PackageArray[] = array();
$Shipping_PackageIndex = sizeof($Shipping_PackageArray)-1;
$Shipping_PackageArray[$Shipping_PackageIndex]["eCart_Quantity"] = (($Shipping_Packaging == 1)?$eCart1->DisplayInfo("Quantity"):1);
$Shipping_PackageArray[$Shipping_PackageIndex]["IsPackage"] = "true";
$Shipping_PackageArray[$Shipping_PackageIndex]["Quantity"] = "".WA_eCart_FormatNumber($eCart1->DisplayInfo('Quantity'), true, 1) ."";
$Shipping_PackageArray[$Shipping_PackageIndex]["WeightUnits"] = "".strtoupper($eCart1->WeightUnits)."S" ."";
$Shipping_PackageArray[$Shipping_PackageIndex]["PackageWeight"] = "".WA_eCart_FormatNumber($eCart1->TotalColumn('TotalWeight'), true, 1) ."";
$Shipping_PackageArray[$Shipping_PackageIndex]["PackageType"] = "02";
$Shipping_PackageArray[$Shipping_PackageIndex]["SizeUnits"] = "IN";
$Shipping_PackageArray[$Shipping_PackageIndex]["PackageLength"] = "0";
$Shipping_PackageArray[$Shipping_PackageIndex]["PackageWidth"] = "0";
$Shipping_PackageArray[$Shipping_PackageIndex]["PackageHeight"] = "0";
//Special Services
}
and on checkout I am always sent to the shipping failure page with the message: S is not a valid unit of measurement for weight for this shipment
I cannot find any reference to WeightUnits as in $eCart1->WeightUnits in the ecart files so how should this info be pulled in or is it a bug ?