Whenever I try to access SSRS 2008 R2 through a URL (i.e. after being published on the net), it always shows a login prompt when accessing the report. The problem does not appea
I'm not sure from you're question is the login box a prompt to get you access to the report server or is it a prompt on the reports datasource.
It sounds a bit like permissions to access the report server, I guess you could try giving the app pool user permissions to access the report server and run the report or use an impersonation account to access the report.