Friend can't grab blocks in the server. Any ideas?

[Silentshot741]

So I started a server today to try out hexxit with my friend. Server works fine and everything but for whatever reason when he breaks a block he can't grab it. I don't know if its a connection issue he's having or anything but if anyone has had the same problem and found a way to fix it, please let me know. Wanna get this thing going so we can start the adventure lol.

[Joker2040]

I've had blocks appear to not be picked up, but I already picked them up, and they're gone when I log out and back in.