Steps to reproduce:
1. Order crates from the console. (Muzzle and webbing crates in that order.)
2. Supply shuttle arrives but is invisible. You can walk around through the "walls" of the shuttle and nothing happens.
3. Send invisible shuttle back to central. Call it back to the Sulaco.
4. Wait for sweet release of death while not expecting to get gibbed. Get gibbed.
Check the status screen to see that the shuttle shuttle is docked at the Sulaco.

Edit: Probable duplicate of this bug: http://colonial-marines.com/viewtopic.php?f=116&t=4228