Employment Law Questions? Ask an Employment Lawyer.
You can absolutely sue your employer. You may be required to exhaust administrative remedies established by the company, or take your dispute before the Equal Employment Opportunity Commission (EEOC) (www.eeoc.gov) prior to filing suit in civil court. Whether you have to do this depends on your company's written policies with regard to employee grievances.
If there are no policies, or after you've gone through the administrative steps, you can file suit in civil court. An employer is not immune from being sued by its employees or anyone else.