ok, this only seems to be on my maps, not other peoples that i download (most of the time) but a couple of seconds after somone joins my server they just disapear!

They could have 1) a bad connection to your server, 2) the server ping may be too great, or 3) your server might become unavailable after they leave, so they can't return. Im not sure if any of those things would work, but those are my most logical guesses. Thats only the problems that I've experienced. :/

[Edit:] Maybe this should go into the Mapping Help forum, if you want to recieve more advice.

ok, your right, could a mod kindly move this?

also, a friend played on my server today and he said that he got a wrong map version error.....

I have the exact same problem with my maps. It's definitely a problem with the map not the server, because it happens to everyone who tries to host a map I've made. It lets them join then after a couple seconds they get kicked with a wrong map version error. I dont know how to fix the problem though, hopefully someone here does.

usually when i get the wrong map version i just rejoin automatically downloading it again