I'd also guess too hot, you can cotrol heat by the amp setting and also by the wire speed (fine adjustments). Also got to remember that the tip should be as close as possible to 90 deg from the work, so you have a good shield gas bubble. You have to look around the tip, not move the tip so you can see. I'm also partial to the cone tips, for most anything under 3/16" and use them all the way up to 3/8" though they do foul a little quicker.
I have trouble with the inside of the noozle getting coated with splatter or dust on occasion and causing problems. A good silicon tip spray really helps, as does a set of tip cleaning brushes.
I don't feel the need to run long contiious beads, I run a couple of inches take a look and let things cool down a bit and then continue. The heat in the material also messes with your AMP settings and affects the nature of the bead.