Add-On Liveries corrupting 747 aircraft.cfg

Hi Everybody,quick question - I just downloaded and installed several add-on liveries from the PMDG website for the FS9 version of the 747.Having installed them, the 747 just disappeared completely from the MSFS aircraft menu - neither the base model nor the add-on liveries were visible. As if I didn't have the 747 at all.So I went looking to see what was wrong. The folder was still there, inclusing all the new texture folders, so I checked the aircraft.cfg and noticed to my dismay that everyhing had been deleted from that file apart from the specific texture section for the last two liveries I installed (Singapore and Quantas). All other data usuall contained i the aircraft.cfg had been deleted!As I stupidly did not back anything up before installing the new liveries, I had to uninstall and completey reinstall the 747 package. Then, having made a back-up of the .cfg file, (yeah yeah, I learned the hard-way!!) I then added the additional textures manually to the file - and it works fine now.Any ideas what caused this file corruption? I simply double-clicked the installers and let them go to work. Anybody else experienced this?Thanks and best regards from EDDFEd