LoadError is a typical error when a library is 'required' but is not
found. I'm not familiar with how textmate uses ruby (although I do
use textmate and the ack bundle). From the error it's probably a
"require 'cgi'" that failed to find the cgi library. Thats normally
part of a standard ruby install.
Go into irb and type "require 'cgi'" and see if that gives you errors