Warnings related to localization

[istream]

I am using TL 1.9.0 in Ubuntu 10.04, apache2, and PostgresdB environment. Everything is working fine, however I see the following in my event log and unable to figure where/what needs to be set to get rid of this warnings. I am only listing a sample below, there are 100s of these, referring to different strings.
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string 'show_eventdetails' is not localized for locale 'en_US'

[fman]

we maintain updated ONLY en_GB strings.txt
if you want to help to maintain updated en_US you are welcome.
You can use our new GIT repository on gitorious => http://gitorious.org/testlink-ga/testlink-code

[istream]

I am afraid, I do not know how to perform this task. If there are some instructions somewhere, I will be glad to do this.
Thanks