The CS F-18 works ok with your install ?
And what you describe happens with any plane ? Not just with few ?

I don't know if there was something wrong with installation or in case you're in OS Win8, but try this :

After you install weapon with the loader (must run both loader & FSX afterwards as administrator), open plane's folder inside FSX and from aiplane's "panel" folder, copy all files except "panel.cfg" and paste them in "panel.csweapon" folder. Run FSX (as admin) & see if it works for you.