Hi Alberto.
This might be due to the release. Windows 2008 brought several improvements and changes when compared to 2003 - there are functionalities that, despite have the same name/goal, are completely different between the two versions. One thing you can try to workaround this issue is to use some third-party tool like BGInfo to print the logged-in username to the desktop background (useful when running a full Desktop session). This way you will know at the beginning of the recording what is the logged in user.
Please remember that Windows Server 2003 is no longer supported by Microsoft, so there is not much we can do here, sadly.
Best Regards,
Renato Pioker