... and then replaced the default entry in /etc/sysconfig/desktop with lxde?
That should not be required to be done by the user as the extension startup file (i.e. '/usr/local/tce.installed/LXDE') does exactly this step at installation time of 'LXDE.tcz'.
OTOH if one installs different WM one after another the content of '/etc/sysconfig/desktop' gets over-written by whichever WM got installed last. In this case I'd suggest to re-run the WM startup file again (as 'root' e.g. via
sudo sh /usr/local/tce.installed/LXDE) or before execution of 'startx'.