Argh!!!!! this is the only thing I can say about pretty much all available plasterboard fixings. Who the hell designs this crap? everything I've tried so far, starting with normal wall plugs, ending on stuff which is supposed to be the bees knees when it comes to plasterboard, just failed terribly. I have become a laughing stock for my wife who thinks I'm not able to fix a bloody coat hanger to a wall on which it was previously attached (but failed due to crap plasterboard fixings put in by the builders). Each fixing type I've tried so far is based on a rather simple idea of plonking a hole in the plasterboard, sticking the plug inside this hole and then tightening the fixing screw until the back end of the plug compresses enough to "grab" the plasterboard from both sides, thus giving you a fixing point. What the designers haven't realised yet is the fact that when you start tightening the screw, the whole damn plug just starts rotating in the plasterboard hole. Of course if it starts rotating, there's no way to tighten the screw to compress the back end, which means you are left with a loose fixing point, rather useless if you want to attach anything to it.
The only thing I've not tried so far is these Grab It fixings:
Which look like might work as they remove the fundamental flaw which is friction based compression. Anyone tried these?