The problem could be with your browser cookies setting
Use Internet Explorer
From your Internet browser click help then click About Internet Explorer
Make sure the version is 6.0 or higher
If version is OK
Click Tools then click internet options
From the Internet options box, click the Privacy tab
Slide down the setting control so that it will accept all cookies
Click OK
Make sure you don't go to any other site excluding adecco (don't open any yahoo page).
Immediately after the test go back to the privacy tab and return the setting to the original form.