Problems with FasterCSV

I'm installing FasterCSV (sudo gem install fastercsv) but when I'm
using it with Rails (in a migration) I get an "uninitialized constant
FasterCSV" error:

rake aborted!
uninitialized constant FasterCSV
./db/migrate//004_add_data.rb:3:in `real_up'

So - in the gem directory when running rake I get a whole bunch of
permission errors like:

  1) Error:
Errno::EACCES: Permission denied - ./test/temp_test_data.csv
    ./test/tc_interface.rb:16:in `initialize'
    ./test/tc_interface.rb:16:in `setup'

but when running sudo rake everything is fine.

Are the two problems (the Rails error and the permission error) related

to each other? When I change the permissions in the gem folder I can
run the tests with no errors, but I still get the "uninitialized
constant FasterCSV"