Catalyst 3750 Web Interface Broken

Question

On a WS-C3750X-24 running software version 12.2(55)SE5 when I try to access the web administration interface with Firefox 17ESR, all I see is an empty 3x4 table with a blue-grey bar at the top and four icons in the first column: a green speech balloon with a check mark in the first and last row, and a yellow triangle with an exclamation mark in the second and third row. No text, no logo, no buttons, no links, no nothing. The yellow triangles link to a page /setup_report.htm but clicking on them just displays the same page again. It doesn't matter if I try http or https.
If I try to open the same page with https in Internet Explorer I get a "This page cannot be displayed" error with the usual unhelpful suggestions. With http, IE thinks for a few seconds, mis-autocorrects the URL by prefixing it with "www." and then displays a blank page.
Apart from that, the switch works fine. I can access and manage it via SSH without a problem. It doesn't log any errors.
What can I do to get the web interface to work?
Thanks,
Tilman

Answer 1

Hi Reza,
thanks for your answer.
The two commands were already in the startup and running configs. I re-entered them nonetheless. Now when I try to access the switch via https, Firefox complains: "Your certificate contains the same serial number as another certificate from this certificate authority. Please acquire a new certificate with a unique serial number. (sec_error_reused_issuer_and_serial)"
The behaviour with http is unchanged.
I also turned both options off ("no ip http ...") and on again. This made no difference.
SDH
Tilman