Changing plugins language in English

Hi There,

I wanted to change some of the words in the buddypress group calendar, so I followed the instructions for translating a plugin. I created the mo file and uploaded it to the language folder and per the instructions in bp_group_calendar.php named it "groupcalendar-[value in wp-config].mo". Now I don't have a value in the wp-config file as I am using wordpress in English, I tried just a made up one, but it didn't work, and then I tried us_EN and it also didn't work. Is there something I am missing out?
I made the same changes to Buddypress. I have renamed "groups" and had no problems with buddypress, so I think I am missing something with the plugins.

Thanks.