Server Disconnect

I am posting this on behalf of someone trying to join my server.

We are using literally the same exact minecraft.jar file. They can start up single-player just fine and play. They always get this message when they try to join my server (which I am currently on as I write this):

Disconnected by Server

This server requires you to have Minecraft Forge installed.

I am running the server (just the two of us) from my Mac and they are trying to join in Windows, could this create problems?

We are running all the latest builds of Redpower 2, Buildcraft, and Industrialcraft 2, as well as Forge and Modloader.

What does the server log say when they join and that happens?

So-and-so [/ip address here] logged in with entity ### at (cords)

But it doesn't say "...joined with: mod list" after that.

In-game it just says "So-and-so has left the game." but never that they actually joined it.

Unsure then, my identical builds work fine on windows and linux I know, but I have never tested a mac.

Ok so I looked at their Modloader and its loading up 3.1.3.107 for some reason.

So we tried to use a copy of my .jar running 3.1.2.94 and it keep booting up with the .107.

We used a fresh .jar, loaded Modloader and 3.1.2.94 into it, and it booted up in .107.

I sent them a copy of my entire .minecraft folder, excluding saves.

It booted up in .107.

Any ideas?

They are not using what you sent them then, they are likely using what their system contains.  That is the *only* thing it could be from what I see.

Hey over mind can you just post a client that works for 1.2.5, im gettign the same problem and if you have one that works id really like to no waste any more time on this. i cant get the flat out client to work and the only mod im attempting at is buildcraft, no addons.

though the plan is after i get that to work to use it on a craftbukkit server.

It is illegal to distribute the MC jar.

It is likely that yours works fine.  It is likely that they are not putting it in the correct place.