Description:
Console login fails for some users, and this does not affect all users on all consoles.
Error: console initialization error: The request failed with http status 400 bad request
Resolution:
To get around this, you can use the IP address of the site server, rather than the name
or:
Add registry DWord values to HKLM\System\CurrentControlSet\Services\HTTP\Parameters
MaxFieldLength 65534
MaxRequestBytes 500000
After adding these values and rebooting the server, all users stopped experiencing HTTP 400 errors.
This information came from the following website.
http://nyc-dba.blogspot.com/2007/04/mysterious-http-400-errors-caused-by.html