This can sometimes happen when you are changing your Display Preferences. To change the default language back to English, click the Options link (the fourth link from the left), then click the Display Preferences link (first link on the right side). There should be a box titled Language. In that drop down list, select English, then click the Submit button at the bottom.
SquirrelMail should now display the webpage in English again! - Updated: June 20, 2002