They haven't gone so far as to glue-up the USB connectors on their PCs, but the Pentagon has temporarily banned removable media of any type. This includes flash memory drives, external hard drives, CDs, devices that can be used as removable media (like an iPod) and so on.
According to Wired, it's a reaction to a worm, Agent.btz, which is spread whenever a new partition or USB drive is detected on the system.
When an infected USB drive is attached to a different PC, it infects that one.
However, this seems to me to be another example of just how inept the Defense Department can be. This worm is 5 months old. Any up-to-date antivirus program can stop it. Yet they have to resort to banning USB drives instead of simply installing and / or updating their antivirus softare.
Seeing as how most consumers have it drummed into their heads that they need antivirus software on their systems, one has to wonder who's running the IT show over there.