error:Premature end of script headers: trac.fcgi

[zhaohu0829@…]

i start the trac with the fcgi, the error will be occure when view a ticket with a big description.but not occure start with standalone!

my trac.fcgi is:

try:
    import os
    import pkg_resources
    if 'TRAC_ENV' not in os.environ and \
       'TRAC_ENV_PARENT_DIR' not in os.environ:
        os.environ['TRAC_ENV'] = '/home/trac'
    if 'PYTHON_EGG_CACHE' not in os.environ:
        if 'TRAC_ENV' in os.environ:
            egg_cache = os.path.join(os.environ['TRAC_ENV'], '.egg-cache')
        elif 'TRAC_ENV_PARENT_DIR' in os.environ:
            egg_cache = os.path.join(os.environ['TRAC_ENV_PARENT_DIR'], 
                                     '.egg-cache')
        pkg_resources.set_extraction_path(egg_cache)
    from trac.web import fcgi_frontend
    fcgi_frontend.run()
except SystemExit:
    raise
except Exception, e:
    print 'Content-Type: text/plain\r\n\r\n',
    print 'Oops...'
    print
    print 'Trac detected an internal error:'
    print
    print e
    print
    import traceback
    import StringIO
    tb = StringIO.StringIO()