Extruding Faces Improperly...

Liku

<div class="IPBDescription">A little something that keeps happening.</div> Ok, I just starting using Milkshape, and I'm trying to model something, but at a certain point, I try to extrude a face, and some of the other faces that should have been created will be missing. Like so[Before/After]:

Obst

Have you had all vertexes welded before extruding?

If yes... ehm... milkshape forum? This is kinda specific >.<