Hope the following helps to narrow down the source of that issue
Until that issue is fixed here is a temporary workaround:
* When the graphical installer asks "Configure the package manager" > "Use a network mirror?" select "No", this will install Gnome from the CD. Otherwise if you select "Yes" that will install Xcfe from the network mirror. This might be the source of the issue?
Downside of that workaround
* If you have a laptop the installer will by default install the "Desktop environment.". The "Laptop" option is not available on the CD :(
* The packages are old. But you can always update them after the install.