A comment that might be helpful. I have run GSX for many years without problem. I use a yoke, throttles, rudder etc. I do not have the full FSUIPC. Yesterday this identical problem appeared. While it is tempting to focus on GSX since the recent update I am pretty sure that Umberto is correct, the problem lies in our individual setups. Whether or not the recent GSX update has triggered this I can't say. In my case I recalled that since my last GSX parking edit quite some time ago I have added a logitech joystick for my airbus. I removed this and immediately the editor functioned, however it continued to freeze during adjusting jetway etc settings. Further checking (note- ensuring no additional controller settings are set to slew isn't enough) I found I had numerous mouse settings that I do not use so I unchecked all of these. The editor immediately functioned faultlessly and I have spent some hours re-setting my parking, jetways etc without difficulty. So just to say that I am fairly sure it is a local problem and it can be overcome by a very thorough check of all controller assignments.
Cheers,
Robert