are you trying to play over lan with someone else or are your trying to connect to an online server.

Over lan assuming you both have the same version I can't see why you would have an issue.

As for online I expect the majority of Unreal servers are running 227h as this is the latest patch from oldunreal.com.

Assuming your using Unreal Gold opposed to the original Unreal install this and you should be able to play on that server at least that is my guess to what your problem is.
http://www.unrealtexture.com/Unreal/Downloads/Patches/227Patch/UnrealGoldPatch227h.zip