I just started my SMP server, but for osme reason, when ever one of my friends tries to place a block, they get kicked. I don't get kicked when i place a block though. Idk how to go about fixing this, any help would be much appreciated! Thanks.
Is he an op? If not, your server software may be thinking something else, and thus kicking him (Minecraft is still in it's beta). It could be that his computer is bad or something. If you're playing using Hamachi, or some other thing to play distantly, he may just be experiencing major lag and be disconnected (I, for one, know that Hamachi is very laggy). Worst case scenario, this is some sot of glitch/bug, and you may not be able to fix it, look around for this type of glitch and see if there are any solutions.
(withouth the - things)