We've just set up a proxy for remote controlling external PC's. We have
a proxy server in the DMZ, we have change the settings in:

Configuration > Device Management > Remote Management > Proxy Settings

When we select a user to Remote control, we click the Remote Control
Task, Select the appropriate IP address, click More options, put the
tick in the "Route Through Proxy" box, but in the proxy dropdown nothing
appears and you can't type in the box either, can anyone shed some light
on this?