If you are facing following error in Share Point 2010
Here it is the solution.
if you are using host header for site, like my server name is siva-pc, so my site is http://siva-pc. but I am using alias for the site as localhost or some other name. so on the server if I am browsing site http://siva-pc on the server I am able to upload the document but if I try to use the host name i.e. http://localhost or other alias name , I am getting above error. If this is true then you need to make sure that you have entry for http://localhost or alias name under central admin -> application management -> configure alternate access mapping. and add http://localhost or alias name into the intranet zone for the http://siva-pc site. And then restart IIS once.
This will resolve your issue.