Mar 11, 2008 10:13 AM|rahul_itpro|LINK
I had a similar problem and i have rectified this thing by changing the integrated windows security checkbox.
To do this goto IIS5.1 management console and then go to your website/virtual directory in IIS under websites folder.
Then right click and goto properties of virtual directory/website. Then goto Directory Security tab and then click Edit button under anonymous control and authentication control and then make sure to check the last checkbox which states Integrated windows
This has solved my problem and hope this will help you.