giulio.detti,
I had a similar problem where the albums were pushed down from the initial paragraph, because of some float issue with my sidebar navigation. The way I resolved it was to find .ngg-albumoverview in the gallery's css, where the statement clear: both was causing the problem. In my site style sheet I added the following:
.ngg-albumoverview { clear: none !important;} /* needed to remove large spacing between top text and first album due to float interactions */
This seemed to take care of the problem. The reason I didn't change to gallery's css was to allow updates of the plugin without the worry of it overwriting the changes I made; hence, the few changes I've made are in a section of my site style sheet marked so I can find it easily.
Hope this helps. Now, I'm hoping to figure out where the freakin' <br /> tag is so I can remove it after <div class="ngg-clear"></div>, 'cause it doesn't need to be there and is adding a line I don't want.
Cheers
Starkers