[Luciano]

ok,
in navbar, and header, as well as footer you have links like to blog.php, archive etc...
instead of pointing to mu-43.com/blog.php or mu-43.com/archive.php
they point to mu-43.com/gallery/blog.php or mu-43.com/gallery/archive.php

To fix this.. you have when you are in acp --> vbgallery --> settings
the first 3 sections...
in the fields you can add the filelinks you want to have a prefix to your forumdirectory..
you can add 1 filename per line..
so in your case, in the navbar replacements I would add

search.php
faq.php
blog.php
blog_search.php
register.php
login.php

to footer replacements
archive/index.php
archive

Now you probably have more links out there that now point to gallery when you are logged in.

PS.. as you have that tab hack.. i do not know if anything has moved from header template to navbar or vice versa...
You would have to test to see if it works when you add the filenames to header replacements or navbar replacements..
L.