Can you take the freebusy URL, paste it in a browser, and download the file? If so, does it look correct?
If that's ok, what is the value for Read URLin the registry key:
HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\O utlook\Options\Calendar\Internet Free/Busy
If that's ok, is it possible you had another freebusy provider installed? What is the value for SMTP in the registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\12.0\ Outlook\SchedulingInformation\FreeBusySupport |