We need to first isolate few things here :-
1) Are you login in from CRM server itself ? - Yes - if you are getting a single prompt and after you enter the credentials you can access CRM this means you do not have the website for which it prompts in local intranet sites. Please add the website
to local intranet sites. Please make sure setting of the browser is set to "automatic login with current user and password"
2) If you are login in from a client machine present in the same domain as CRM server? Yes - Please follow above suggestion
If you get 3 prompts and even after you enter credentials and get 401 error this means SPNs are not set properly on the account running your crm app pool.
3) If the SPNs are set properly but still you get 401 then Set useAppPoolCredentials attribute to TRUE in IIS on CRM server if you have a custom crm app pool account and SPNs are set on app pool.
4)If the multiple prompts comes only from server but from all other machines it works all fine ? Yes - Disable Loop back check by adding BackConnectionHostNames reg key on CRM server or DisableLoopbackCheck reg key. follow below article to set these keys.
http://support.microsoft.com/kb/896861?wa=wsignin1.0
If you get a prompt and after you enter the credentials this means
Arpita
