If it gets that far in the zdesktop log, that means your reverse proxy already works for some URLs but not all. It's choking on the URL /home*. This is not that uncommon because apache mod_proxy config can be very URL specific.
You can try this. After using webclient to login, in the browser window try this URL:
http://<proxy-host-port>/home/~/?fmt=sync&nohdr=1&id=47903
It will probably choke the same way.