I tried loading up my Reporting Services 2005 on my visra machine today via url:
http://localhost/reports/Pages/Folder.aspx
And 
it loaded up blank which i means i couldn't see my Report Folders and DataSources etc but i ccould see the menu like home,my subscribtion etc..
So i taught let me give the Report Server a try at http://localhost/ReportServer and i go an error insufficent permission
I was too sure it was a permission issue so i checked IIS and made sure Windows Auth was enable and Anonymouse access was disabled for the virtual directories Reports and ReportSever.
But still no luck.Also made sure the ReportManager and the Reports folder had the right access.
But i remembered that with vista even when loading Visual Studio its always better to right click and RUN AS ADMIN unless you won't get anything.So i did the same for Internet Exploer and loaded the Reports page and it worked. 
I later found james blog that explained in detail and shows how you can access it without running as admin.
Hope that helps 