I've only had that when either injecting A LOT of gear, or if I accidentally pull the needle out just a little and move it around during the injection.
Make sure you have a long enough needle to get deep into the muscle. I almost always use a 1.5 22g and I really never have a problem with this... but it has happened to me in the past.
i have had it happen if the muscle was not tatally relaxed. has not happened in a while though. yea i would say the same just make sure the needle is long enough