SG500 can't ping gateway from some ports

I've got a stacked SG500. On stack-1, many of the ports, despite being configured the same as others, don't seem to go anywhere other than the switch. I can ping the switch (from a statically set workstation), but nothing else. As far as I can tell, ports (For instance) 4 and 19 have the same configuration but port 4 won't return a ping other than the switch's ip.