I've been trying my hand at building maps for TF2 in Hammer lately, with little success. I'm not new to level development, I've worked quite extensively in the UDK, but there are some things I just can't seem to get working. My biggest problem is, that after I run a map and open it in a local server, the game just behaves strangely. Movement is halted, it becomes difficult to move through water, I can run straight over ledges and just float as though I've turned off clipping entirely. I had thought this was a problem with the maps I was building, but when I tried to load up a map I know works (cp_freight) and play it locally, I got the same issues. My PC is no slouch, either. I can run animations in Maya in real time 30 fps while streaming HD video and keeping Photoshop open in the background just because I'm too lazy to close it. Does anybody have any ideas?