Railcraft Error: Disconnected when railcraft is used

[Than2000]

HELP!!! I run a tekkit classic server, and everything is pretty much normal and it runs fine. When I craft items, they appear in the outcome box, and they are visible in NEI. But when I try to take certain things from railcraft, like coke oven brick, out into Minecraft itself by crafting them or spawning them in, I am disconnected from the server!!! It just says Connection Lost: End of Stream. On the console, it says Than2000 (me) lost connection: disconnect.genericReason. the weirdest thing is, they appear on NEI, and in the crafting box; but it's when I take them into the world itself that I'm disconnected. It only seemed to be railcraft stuff, so I looked in the mods folder, and there wasn't any railcraft server file! I downloaded railcraft server 1.2.5 and put it in, but now the server won't start with "java.lang.NoClassDefFoundError: BaseMod" and a million other lines of junk. I've redownloaded tekkit and the server. Neither helped.  Please help!!! If anyone has had this error, please respond!