If you have many RSS feed registrations in Outlook 2007, you may have noticed that at some point newly added RSS feeds start disappearing. They are added successfully, but on the next restart of Outlook, the registration is just gone.
You can work around this by setting the registry key DisableRoaming in HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\RSS to 1. If this key is not yet present, create it with a type of DWORD.
You'll have to restart Outlook for the change to take effect.
But be cautious: I don't know which side-effects this registry might have.