Sounds like you've run into that infamous Thunar bug. See:
Then change the "AutoMount=true" part to "AutoMount=false".
sudo leafpad /usr/share/gvfs/mounts/network.mount
You'll then want to start Thunar with:
I think one of the above links has a .desktop file with this that you can just put into ~/.config/autostart and that will fix that.
gvfs-mount network: > /dev/null && gvfs-ls network: > /dev/null