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