I have tried printing a UPS shipping label and am seeing an error returned:
120608: Package weight is required
The error indicates that the system was not able to indicate a weight for the order, which means the order weight was 00.00 at the time when the shipping label was printed.
As all orders must have weight present, make sure your items have weights added via My Inventory > Edit Item > Postage Definition.
Alternatively, you can assign weights to your packaging groups and the packaging weight will then be used for the order. (Shipping > Packaging groups)
Please note: Manual recalculation of the order weight section will always be taken as a priority over the weight values assigned to items in the item's postage definition. If you need the system to recalculate the order weight based on the item and packaging weights, edit the order and click Recalculate button: