If you need to reset the language to default (english), then you may upload your tools.php file (in the do_not_upload directory) into your admincp, point your browser to it, and reupload the language. I would suggest backing up your database prior to doing this in case it isn't what you are asking about.
Lynne:
Thanks. I will do as recommended with backing it up first. I think this will solve my problem hopefully!