Interface "UP" but not "RUNNING"

We have kind of a stumper, but I'm hoping somebody might be able to
shed some light...

We have a server with a an Intel dual-interface NIC (running RedHat
7.3). We had both interfaces working normally at one time, but we
recently rebooted and the second port never started talking. When we
run ifconfig, we get this for the interface...

eth3 Link encap:Ethernet HWaddr 00:02:B3:BE:2E:86
inet addr:x.x.x.x Bcast:x.x.x.x Mask:x.x.x.x
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:316 errors:0 dropped:0 overruns:316 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:13272 (12.9 Kb)
Interrupt:3 Base address:0x3000

Here's the config file for the interface...

DEVICE=eth3
BOOTPROTO=static
BROADCAST=x.x.x.255
IPADDR=x.x.x.x
NETMASK=x.x.x.x
NETWORK=x.x.x.0
ONBOOT=yes

Here's the output for the working interface...

eth2 Link encap:Ethernet HWaddr 00:02:B3:BE:2E:85
inet addr:x.x.x.x Bcast:x.x.x.x Mask:x.x.x.x
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:69568 errors:0 dropped:0 overruns:0 frame:0
TX packets:71019 errors:0 dropped:0 overruns:1 carrier:0
collisions:0 txqueuelen:100
RX bytes:16372882 (15.6 Mb) TX bytes:42147013 (40.1 Mb)
Interrupt:5 Base address:0x1000

--Notice that there isn't a "RUNNING" between "BROADCAST" and "MULTI"
(what does "RUNNING" mean exactly anyway? There's some documentation
that suggests it means that the interface is "recognized by the host",
but that doesn't seem to apply.)
--There don't seem to be any errors in dmesg or any of the logs.
--When I look at /proc/pci, I don't see any messages that suggest an
unrecognized device.
--The other interface on the same card is working fine.
--We can ping the address that's bound to eth3 from the local host, or
any other host that isn't on the same segment as eth3.
--In the bootup messages the OS does recognize eth3 as being present.
--There's no link light on the eth3 port.

What are we missing here? Any help will be greatly appreciated! (If
possible, feel free to email this reply as it's sometimes hard to keep
up with the traffic on this very busy list. Thank you!)