That usually means you didn't inject deep enough or maybe into some scar tissue. Use a larger needle(1.5"), or pull the sking taut while injecting then let go when done...
if some stuff comes back out after inject it usually means you injected too close to the skin (and probably not in the muscle!!) - it basically means you are waisting your gear!
get the needle deep into the muscle (using a 1 inch or better: a 1.5 inch needle for the glutes)
Check out 2thick's website on elite for good info...