loading jquery twice to make something work, is that ok ?

loading jquery twice to make something work, is that ok ?

Hi,
i'm starting using jquery, and I have some kind of problem.

I develop most of my sites using Wordpress as CMS, with the popular Nextgen-gallery as image management-plugin. This works very nice and is a powerful combination.

Now, since Nextgen already uses jquery and makes sure the library is loaded in the header, there should be no need to load it again to perform some of my functions. Yet, the only way it works is when I DO load jquery again for my functions..

This isn't normal, right?
Why can't I just use the library Nextgen has already loaded. (note: this is not only with nextgen the case).

Who can help me with this ?

example site: http://www.manager-tv.be/ (see source)