All I am saying is if you have navtabs that have relative links to files you want them to be full urls so the files can be found. We are talking basic html 101 here. A relative link means look for the file in the current directory structure your in hense your issue because your telling the navbar to look for vbquiz.php hack in your gallery directory because it uses a relative url to that file instead of a full url.
well the answer would be what I have already stated before. whatever hacks or mods your using you want to correct any relative urls to files to be full urls so files can be found. I know nothing about any hacks or mods your running so not like I can tell you where to change anything. You would need to find that reference in whatever mod your using and correct that relative url. None of these would be issues with the gallery. Your referencing mod issues and support for mods can be obtained through the mod thread you downloaded the mod from.