Weird Sanctum Multiplayer Problem

Hey guys, I have a really peculiar problem with Sanctum 1, and searching for it hasn't been fruitful, hoping to get some help here. My friend and I recently got Sanctum to co-op it, the problem I have, is that when I join his game, (or any other server), I can't place anything other than blocks. When we start the game, I choose my towers and weapons, but can't place anything other than blocks. On his side, he can see the holograms of the things I wanna place, but when I hold a gattling gun over a block, it doesn't do anything, the hologram just disappears for me, trying to build it doesn't give any errors or indication that it's working.

I wish this were the only problem, I can at least upgrade my guns, but when the match starts, I can see the monsters spawning, but they stand absolutely still on my end, while they're moving around on my friend's game. I end up having to shoot invisible monsters that are smacking me about, making me useless in the game.

I'm running Windows 7 Ultimate 64-bit, updated drivers, re-installed the game, tried having my friend join my game, which he either doesn't see, or when he does, has the game crash when it tries to join. Could really use some help, thanks. Oh, and Happy Holidays!