If you ever have problems with terrain not painting texture wise (doesn't always happen, but often, may be the root cause of your "media importing" problem) go into camera mode, move it at least 64uu up and then back down and then rebuild.
Don't ask why, it fixes it every time. If you ever open your map and find your terrain is displaying its normal map rather than its diffuse, open the terrain editor and open every material folder in sequence and then close them all. Rebuild. Terrain seems to be a twitchy thing, though when it works it looks quite good.
According to several forum posts, the LadderVolume doesn't work. I don't seem to be able to replicate one using gravity or water volumes either.
~14 months experience mapping with UE3
Athlon64 2.7gHz->OC 3.9gHz, 31C, MSi 9500GT->OC 1gHz core/2gHz memory, 48C, 4Gb DDR2 667, 500Gb Seagate + 80Gb Maxtor + 40Gb Maxtor = 620Gb, XP Home
Air cooled, total cost £160