I'm having the same problem.
I use mXcomment 1.0.7 but i also use Simple Image Gallery for my pictures in articles.
It does'nt work together.
mXcomment overrules the gallery so there aren't any pictures to be seen.
Unless i place them in a separate catagory wich isn't assinged to mXcomment.
But as soon as i place the {mxc} tag in mij article next to {gallery}image{/picture} the images are gone and i see the tag instead.
It makes no difference if i place the {mxc} before or after the other tag.
Please help or i will be forced to use another comment component, but i don't want that.
I really love mXcomment but i also need the gallery.