Make sure you are initiating your print by right-clicking the item and selecting PRINT LABELS; as that option is more effective than the PRINT LABELS button at the bottom of the shipment grid.  (To right-click on a MAC press CONTROL and click your mouse at the same time.)  Right-clicking to print will print the label(s) for the particular item instead of the button at the bottom which prints all of them at once.  We have found that attempting to print all of them at once can be too much for larger shipments and stall your browser.