I just downloaded the beta, got in to the game by steam, connected to a sever then this comes up "your .dll [cl_dlls\client.dll] differs from the sever's" i have try alot of diffrent severs why is this?? will have have to uninstall and reinstall ?

probably you haven't installed the beta 3.
as it is said in
http://www.natural-selection.org/downloads.html
first make sure you have installed NS beta 1 (150 MB)
then download and install NS beta 3 patch (25 MB)

Note: For the topic title, you can write more descriptive words, title is the brief introduction to what you are going to say and from "Not working help" I do not understand what you are going to talk about and I can't understand the thing that is not working. You may have used more descriptive words such as "client.dll differs error", "your .dll [cl_dlls\client.dll] differs from the sever" etc.

Also, this message should not be in the "beta bug report" forum, you should have sent it to the "TECH SUPPORT" FORUM.