If Skype is installed on the same machine as LabTutor Server, this may result in ports 80 & 443 being used by Skype, and therefore not being available for use by LabTutor Server.
It is possible to work around this problem without having to either uninstall Skype or reduce its standard functionality.
Open Skype and click Tools > Options > Advanced > Connection. Untick the box that says Use port 80 and 443 as alternatives for incoming connections. Please note that restarting the computer may be required for any changes to port settings to take effect.
VMWare Sever also has the same issues, and should not be installed on the same machine as LabTutor Server.
This information is valid for LabTutor v4.0 or later.