Sorry. Forgot the specs. Okay...
Vista SP1 64-bit
Now then, as an example of sceneries that didn't work, take the folder in C:\Program Files (x86)\Microsoft Games\Flight Simulator 9\Addon Scenery named "FlyTampa - Seattle" for instance.
I go into FS9, open up my scenery menu, go to addon scenery cache listing and click Add Area.. and click the folder FlyTampa - Seattle and then add. It appears on the list as enabled with a check in the box. I do not have "Clear CD" selected, and so I'll repeat the process with other scenery files and once they're all set in the list, I restart the program to allow the changes to take place.
Well, when I come back, its as if I had done nothing before and its right back to the listing of default sceneries. Is there a limit to how much you can add or something?
No limit That I am aware of - your issue sounds as if you do not have your Vista permissions set to allow such changes.
Try turning off UAC and see if that allows the chnages to stick -
Start -> Control Panel -> User Accounts and turn off UAC (User Account Control). That is a universal option which will of course remove any protection on your entire system.
Also be sure you are running as Adminstrator.