rake aborted on ubuntu

[srinath]

Hi,
I was got this error when trying to install adva_cms .
Using ruby - 1.8.6 , rails - 2.3.4 (also had 2.3.5) and all gems on Ubuntu .

Checking out files: 100% (2977/2977), done.
executing git checkout -b tag/0.3.0 0.3.0 from /home/srinath/adva_cms/vendor/adva
Switched to a new branch "tag/0.3.0"
rake adva:install:core -R vendor/adva/engines/adva_cms/lib/tasks
rake aborted!
undefined method `unix?' for #Rake::Application:0xb7d72e38

(See full trace by running task with --trace)
rake adva:assets:install
rake aborted!
Don't know how to build task 'adva:assets:install'

(See full trace by running task with --trace)
applied http://github.com/svenfuchs/adva_cms/raw/master/templates/adva-cms.0.3.0.rb
srinath@srinath-laptop:~$

Could you please tell how to solve this issue and run , i'm interested to run this cms for my project .
thanks.