You certainly don't want to create a new repository for it. Creating a version in another language is more than just translating all the strings (eg layout issues, Unicode bugs, installer changes, etc), and it's very likely that you'll discover some bugs in your codebase in the process. So you'll want those bug fixes to go back into the original project. This would be very difficult if you create a separate repository.
I would suggest creating a translation branch in your main repository to allow you to do the translation work, and get the program stabilised. Also test the original language version to ensure that you haven't introduced bugs into that. Once they're both stable then merge them back to the trunk.
EDIT: the OP has clarified that this is referring to a new programming language. I'd still recommend using the same repository, but perhaps on a new branch, or change the repository layout so that you have multiple trunks (ie /Project1/[trunk|branches|tags]
, /Project2[trunk|branches|tags]
)