having problem with script/server, and other pathes

when i input script/server i get this error i have just recently been
experiencing this problem. i recently fixed the problem with starting
rails, and it not working now i get this new error and its bugging me.
if anyone can help me that would be great thanks in advance
./script/../config/boot.rb:18:in `require': No such file to load --
rubygems (LoadError)
        from ./script/../config/boot.rb:18
        from script/server:2:in `require'
        from script/server:2