by Luis de Vasconcelos.
It seems to be happening a lot lately. Example: see the Images do not display on my moodle site and Missing icons and images discussions.
Turning off the 'Use slash arguments' option under Site administration / Server / HTTP fixed it for me on my IIS 6 / MSSQL / WinXP dev machine. But I've got a niggly feeling that something else is invloved...