How to solve gem conflict error? - Ruby/Rails

Trying to run gem install slickgrid-rails it shows:

ERROR: While executing gem ... (Gem::DependencyResolutionError) conflicting dependencies actionpack (~> 3.1.0) and actionpack (= 3.0.0) Activated actionpack-3.0.0 which does not match conflicting dependency (~> 3.1.0)

Conflicting dependency chains:

slickgrid-rails (>= 0), 0.3.1 activated, depends onrailties (~> 3.0), 3.0.0 activated, depends onactionpack (= 3.0.0), 3.0.0 activated

versus:

slickgrid-rails (>= 0), 0.3.1 activated, depends onsass-rails (>= 0), 3.1.0 activated, depends onactionpack (~> 3.1.0)

Any suggestion?