E4200 firmware upgrade problem

Hello,

When I try to upgrade the firmware of my E4200, I get the following error:

400 Bad Request

No request found.

I get this error message when I try to load the page to update the firmware, so even before I get the opportunity to upload the new firmware file. The url is http://192.168.1.1/Upgrade.asp

Can anyone help me with this? Linksys support won't help me because the router is older than 90 days.

Thanks