Please tell me how to change the language used in comments

Hello,

Hello,
I'm editing a Word document 2007 for which the language is US English but, for some reason, when I try to add a comment, the language is Saudi Arabia Arabic.

Word help tells me to use "Styles" to change the language for comment text, but it doesn't seem to work. I go to Styles, choose "Comment Text" and "Modify," then press the "Format" button, select "Language" and choose US English from the dropdown box, but it doesn't change the language. When I try to add a comment, the language is still Saudi Arabia Arabic and my typing is backwards.

Please, if anyone can help me with this problem, I will appreciate it very much.

Thank you.