Its observed at times that SEPM login fails and the Error code generated found in scm-server-0.log at : C:\Program Files\Symantec\Symantec Endpoint Protection Manager\Tomcat\logs. Hope this would help to resolve the issue.
Hello Ivan, I agree to your point that there are multiple reasons for this error. Based on the scenario we will need to proceed. Re-installation of IIS may be one of the resolutions however, it is completely based on scenario. Please refer to the following link for detailed info on Http 400 Error http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/64e30660-d2f0-4e90-98cc-1652214a2b93.mspx?mfr=true On this link you would be able to see other Http errors also. Thanks :)