Freezing rails applications

Hi,
     I have installed RAILS 2.0 in my machine. When I was freezing my
rails application for rails 1.2.3. it is giving me the following
error.

(in D:/ruby/reference_code/ublic_database/ublic_database/
ublip_project)
rake aborted!
no such file to load -- rcov/rcovtask
D:/ruby/reference_code/ublic_database/ublic_database/ublip_project/
rakefile:10
(See full trace by running task with --trace)

please help.

Pavan